server/peer.c, etc.: Introduce who-goes-there protocol.

[tripe] / server / tripe.h

/* -*-c-*-
 *
 * Main header file for TrIPE
 *
 * (c) 2001 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of Trivial IP Encryption (TrIPE).
 *
 * TrIPE is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 3 of the License, or (at your
 * option) any later version.
 *
 * TrIPE is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with TrIPE.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef TRIPE_H
#define TRIPE_H

#ifdef __cplusplus
  extern "C" {
#endif

/*----- Header files ------------------------------------------------------*/

#include "config.h"

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>

#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#include <pwd.h>
#include <grp.h>

#ifdef HAVE_LIBADNS
#  define ADNS_FEATURE_MANYAF
#  include <adns.h>
#endif

#include <mLib/alloc.h>
#include <mLib/arena.h>
#include <mLib/base64.h>
#ifndef HAVE_LIBADNS
#  include <mLib/bres.h>
#endif
#include <mLib/codec.h>
#include <mLib/daemonize.h>
#include <mLib/dstr.h>
#include <mLib/env.h>
#include <mLib/fdflags.h>
#include <mLib/fdpass.h>
#include <mLib/fwatch.h>
#include <mLib/hash.h>
#include <mLib/macros.h>
#include <mLib/mdup.h>
#include <mLib/mdwopt.h>
#include <mLib/quis.h>
#include <mLib/report.h>
#include <mLib/sel.h>
#include <mLib/selbuf.h>
#include <mLib/sig.h>
#include <mLib/str.h>
#include <mLib/sub.h>
#include <mLib/trace.h>
#include <mLib/tv.h>
#include <mLib/versioncmp.h>

#include <catacomb/buf.h>
#include <catacomb/ct.h>

#include <catacomb/chacha.h>
#include <catacomb/gaead.h>
#include <catacomb/gcipher.h>
#include <catacomb/gmac.h>
#include <catacomb/grand.h>
#include <catacomb/latinpoly.h>
#include <catacomb/key.h>
#include <catacomb/paranoia.h>
#include <catacomb/poly1305.h>
#include <catacomb/salsa20.h>

#include <catacomb/noise.h>
#include <catacomb/rand.h>

#include <catacomb/mp.h>
#include <catacomb/mpmont.h>
#include <catacomb/mprand.h>
#include <catacomb/dh.h>
#include <catacomb/ec.h>
#include <catacomb/ec-raw.h>
#include <catacomb/ec-keys.h>
#include <catacomb/x25519.h>
#include <catacomb/x448.h>

#include "priv.h"
#include "protocol.h"
#include "slip.h"
#include "util.h"

#undef sun

/*----- Magic numbers -----------------------------------------------------*/

/* --- Trace flags --- */

#define T_TUNNEL 1u
#define T_PEER 2u
#define T_PACKET 4u
#define T_ADMIN 8u
#define T_CRYPTO 16u
#define T_KEYSET 32u
#define T_KEYEXCH 64u
#define T_KEYMGMT 128u
#define T_CHAL 256u
/* T_PRIVSEP  in priv.h */

#define T_ALL 1023u

/* --- Units --- */

#define SEC(n) (n##u)
#define MIN(n) (n##u * 60u)
#define F_2P32 (65536.0*65536.0)
#define MEG(n) (n##ul * 1024ul * 1024ul)

/* --- Timing parameters --- */

#define T_EXP MIN(60)                   /* Expiry time for a key */
#define T_REGEN MIN(40)                 /* Regeneration time for a key */

#define T_VALID SEC(20)                 /* Challenge validity period */
#define T_RETRYMIN SEC(2)               /* Minimum retry interval */
#define T_RETRYMAX MIN(5)               /* Maximum retry interval */
#define T_RETRYGROW (5.0/4.0)           /* Retry interval growth factor */

#define T_WOBBLE (1.0/3.0)              /* Relative timer randomness */

#define T_WGT 5                         /* Age for who-goes-there */

/* --- Other things --- */

#define PKBUFSZ 65536

/*----- Cipher selections -------------------------------------------------*/

typedef struct keyset keyset;
typedef struct algswitch algswitch;
typedef struct kdata kdata;
typedef struct admin admin;

typedef struct dhgrp {
  const struct dhops *ops;
  size_t scsz;
} dhgrp;

typedef struct dhsc dhsc;
typedef struct dhge dhge;

enum {
  DHFMT_STD,                /* Fixed-width format, suitable for encryption */
  DHFMT_HASH,                /* Deterministic format, suitable for hashing */
  DHFMT_VAR                    /* Variable-width-format, mostly a bad idea */
};

typedef struct deriveargs {
  const char *what;                     /* Operation name (hashed) */
  unsigned f;                           /* Flags */
#define DF_IN 1u                        /*   Make incoming key */
#define DF_OUT 2u                       /*   Make outgoing key */
  const gchash *hc;                     /* Hash class */
  const octet *k;                       /* Pointer to contributions */
  size_t x, y, z;                       /* Markers in contributions */
} deriveargs;

typedef struct bulkalgs {
  const struct bulkops *ops;
} bulkalgs;

typedef struct bulkctx {
  const struct bulkops *ops;
} bulkctx;

typedef struct bulkchal {
  const struct bulkops *ops;
  size_t tagsz;
} bulkchal;

typedef struct dhops {
  const char *name;

  int (*ldpriv)(key_file */*kf*/, key */*k*/, key_data */*d*/,
                kdata */*kd*/, dstr */*t*/, dstr */*e*/);
        /* Load a private key from @d@, storing the data in @kd@.  The key's
         * file and key object are in @kf@ and @k@, mostly in case its
         * attributes are interesting; the key tag is in @t@; errors are
         * reported by writing tokens to @e@ and returning nonzero.
         */

  int (*ldpub)(key_file */*kf*/, key */*k*/, key_data */*d*/,
               kdata */*kd*/, dstr */*t*/, dstr */*e*/);
        /* Load a public key from @d@, storing the data in @kd@.  The key's
         * file and key object are in @kf@ and @k@, mostly in case its
         * attributes are interesting; the key tag is in @t@; errors are
         * reported by writing tokens to @e@ and returning nonzero.
         */

  const char *(*checkgrp)(const dhgrp */*g*/);
        /* Check that the group is valid; return null on success, or an error
         * string.
         */

  void (*grpinfo)(const dhgrp */*g*/, admin */*a*/);
        /* Report on the group to an admin client. */

  T( void (*tracegrp)(const dhgrp */*g*/); )
        /* Trace a description of the group. */

  int (*samegrpp)(const dhgrp */*g*/, const dhgrp */*gg*/);
        /* Return nonzero if the two group objects represent the same
         * group.
         */

  void (*freegrp)(dhgrp */*g*/);
        /* Free a group and the resources it holds. */

  dhsc *(*ldsc)(const dhgrp */*g*/, const void */*p*/, size_t /*sz*/);
        /* Load a scalar from @p@, @sz@ and return it.  Return null on
         * error.
         */

  int (*stsc)(const dhgrp */*g*/,
               void */*p*/, size_t /*sz*/, const dhsc */*x*/);
        /* Store a scalar at @p@, @sz@.  Return nonzero on error. */

  dhsc *(*randsc)(const dhgrp */*g*/);
        /* Return a random scalar. */

  T( const char *(*scstr)(const dhgrp */*g*/, const dhsc */*x*/); )
        /* Return a human-readable representation of @x@; @buf_t@ may be used
         * to hold it.
         */

  void (*freesc)(const dhgrp */*g*/, dhsc */*x*/);
        /* Free a scalar and the resources it holds. */

  dhge *(*ldge)(const dhgrp */*g*/, buf */*b*/, int /*fmt*/);
        /* Load a group element from @b@, encoded using format @fmt@.  Return
         * null on error.
         */

  int (*stge)(const dhgrp */*g*/, buf */*b*/,
              const dhge */*Y*/, int /*fmt*/);
        /* Store a group element in @b@, encoded using format @fmt@.  Return
         * nonzero on error.
         */

  int (*checkge)(const dhgrp */*h*/, const dhge */*Y*/);
        /* Check a group element for validity.  Return zero if everything
         * checks out; nonzero on failure.
         */

  int (*eq)(const dhgrp */*g*/, const dhge */*Y*/, const dhge */*Z*/);
        /* Return nonzero if @Y@ and @Z@ are equal. */

  dhge *(*mul)(const dhgrp */*g*/, const dhsc */*x*/, const dhge */*Y*/);
        /* Multiply a group element by a scalar, resulting in a shared-secret
         * group element.  If @y@ is null, then multiply the well-known
         * generator.
         */

  T( const char *(*gestr)(const dhgrp */*g*/, const dhge */*Y*/); )
        /* Return a human-readable representation of @Y@; @buf_t@ may be used
         * to hold it.
         */

  void (*freege)(const dhgrp */*g*/, dhge */*Y*/);
        /* Free a group element and the resources it holds. */

} dhops;

typedef struct bulkops {
  const char *name;

  bulkalgs *(*getalgs)(const algswitch */*asw*/, dstr */*e*/,
                       key_file */*kf*/, key */*k*/);
        /* Determine algorithms to use and return a @bulkalgs@ object
         * representing the decision.  On error, write tokens to @e@ and
         * return null.
         */

  T( void (*tracealgs)(const bulkalgs */*a*/); )
        /* Write trace information about the algorithm selection. */

  int (*checkalgs)(bulkalgs */*a*/, const algswitch */*asw*/, dstr */*e*/);
        /* Check that the algorithms in @a@ and @asw@ are acceptable.  On
         * error, write tokens to @e@ and return @-1@; otherwise return zero.
         */

  int (*samealgsp)(const bulkalgs */*a*/, const bulkalgs */*aa*/);
        /* If @a@ and @aa@ represent the same algorithm selection, return
         * nonzero; if not, return zero.
         */

  void (*alginfo)(const bulkalgs */*a*/, admin */*adm*/);
        /* Report on the algorithm selection to an admin client: call
         * @a_info@ with appropriate key-value pairs.
         */

  size_t (*overhead)(const bulkalgs */*a*/);
        /* Return the per-packet overhead of the bulk transform, in bytes. */

  size_t (*expsz)(const bulkalgs */*a*/);
        /* Return the total size limit for the bulk transform, in bytes,
         * after which the keys must no longer be used.
         */

  bulkctx *(*genkeys)(const bulkalgs */*a*/, const deriveargs */*a*/);
        /* Generate session keys and construct and return an appropriate
         * context for using them.  The offsets @a->x@, @a->y@ and @a->z@
         * separate the key material into three parts.  Between @a->k@ and
         * @a->k + a->x@ is `my' contribution to the key material; between
         * @a->k + a->x@ and @a->k + a->y@ is `your' contribution; and
         * between @a->k + a->y@ and @a->k + a->z@ is a shared value we made
         * together.  These are used to construct (up to) two collections of
         * symmetric keys: one for outgoing messages, the other for incoming
         * messages.  If @a->x == 0@ (or @a->y == a->x@) then my (or your)
         * contribution is omitted.
         */

  bulkchal *(*genchal)(const bulkalgs */*a*/);
        /* Construct and return a challenge issuing and verification
         * context with a fresh random key.
         */

  void (*freealgs)(bulkalgs */*a*/);
        /* Release an algorithm selection object.  (Associated bulk
         * encryption contexts and challenge contexts may still exist and
         * must remain valid.)
         */

  int (*encrypt)(bulkctx */*bc*/, unsigned /*ty*/,
                 buf */*b*/, buf */*bb*/, uint32 /*seq*/);
        /* Encrypt the packet in @b@, with type @ty@ (which doesn't need
         * encoding separately) and sequence number @seq@ (which must be
         * recoverable by @decrypt@), and write the result to @bb@.  On
         * error, return a @KSERR_...@ code and/or break the output buffer.
         */

  int (*decrypt)(bulkctx */*bc*/, unsigned /*ty*/,
                 buf */*b*/, buf */*bb*/, uint32 */*seq*/);
        /* Decrypt the packet in @b@, with type @ty@, writing the result to
         * @bb@ and storing the incoming (claimed) sequence number in @seq@.
         * On error, return a @KSERR_...@ code.
         */

  void (*freectx)(bulkctx */*a*/);
        /* Release a bulk encryption context and the resources it holds. */

  int (*chaltag)(bulkchal */*bc*/, const void */*m*/, size_t /*msz*/,
                 uint32 /*seq*/, void */*t*/);
        /* Calculate a tag for the challenge in @m@, @msz@, with the sequence
         * number @seq@, and write it to @t@.  Return @-1@ on error, zero on
         * success.
         */

  int (*chalvrf)(bulkchal */*bc*/, const void */*m*/, size_t /*msz*/,
                 uint32 /*seq*/, const void */*t*/);
        /* Check the tag @t@ on @m@, @msz@ and @seq@: return zero if the tag
         * is OK, nonzero if it's bad.
         */

  void (*freechal)(bulkchal */*bc*/);
        /* Release a challenge context and the resources it holds. */

} bulkops;

struct algswitch {
  const gchash *h; size_t hashsz;       /* Hash function */
  const gccipher *mgf;                  /* Mask-generation function */
  bulkalgs *bulk;                       /* Bulk crypto algorithms */
};

struct kdata {
  unsigned ref;                         /* Reference counter */
  struct knode *kn;                     /* Pointer to cache entry */
  uint32 id;                            /* The underlying key's id */
  char *tag;                            /* Full tag name of the key */
  dhgrp *grp;                           /* The group we work in */
  dhsc *k;                              /* The private key (or null) */
  dhge *K;                              /* The public key */
  time_t t_exp;                         /* Expiry time of the key */
  algswitch algs;                       /* Collection of algorithms */
};

typedef struct knode {
  sym_base _b;                          /* Symbol table intrusion */
  unsigned f;                           /* Various flags */
#define KNF_BROKEN 1u                   /*   Don't use this key any more */
  struct keyhalf *kh;                   /* Pointer to the home keyhalf */
  kdata *kd;                            /* Pointer to the key data */
} knode;

#define MAXHASHSZ 64                    /* Largest possible hash size */

#define HASH_STRING(h, s) GH_HASH((h), (s), sizeof(s))

extern const dhops dhtab[];
extern const bulkops bulktab[];

/*----- Data structures ---------------------------------------------------*/

/* --- The address-family table --- */

#define ADDRFAM(_)                                                      \
  _(INET,       want_ipv4)                                              \
  _(INET6,      want_ipv6)

enum {
#define ENUM(af, qf) AFIX_##af,
  ADDRFAM(ENUM)
#undef ENUM
  NADDRFAM
};

extern const struct addrfam {
  int af;
  const char *name;
#ifdef HAVE_LIBADNS
  adns_queryflags qf;
#endif
} aftab[NADDRFAM];

/* --- Socket addresses --- *
 *
 * A magic union of supported socket addresses.
 */

typedef union addr {
  struct sockaddr sa;
  struct sockaddr_in sin;
  struct sockaddr_in6 sin6;
} addr;

/* --- Mapping keyed on addresses --- */

typedef struct addrmap {
  hash_table t;
  size_t load;
} addrmap;

typedef struct addrmap_base {
  hash_base b;
  addr a;
} addrmap_base;

/* --- Sequence number checking --- */

typedef struct seqwin {
  uint32 seq;                           /* First acceptable input sequence */
  uint32 win;                           /* Window of acceptable numbers */
} seqwin;

#define SEQ_WINSZ 32                    /* Bits in sequence number window */

/* --- A symmetric keyset --- *
 *
 * A keyset contains a set of symmetric keys for encrypting and decrypting
 * packets.  Keysets are stored in a list, sorted in reverse order of
 * creation, so that the most recent keyset (the one most likely to be used)
 * is first.
 *
 * Each keyset has a time limit and a data limit.  The keyset is destroyed
 * when either it has existed for too long, or it has been used to encrypt
 * too much data.  New key exchanges are triggered when keys are close to
 * expiry.
 */

enum { DIR_IN, DIR_OUT, NDIR };

struct keyset {
  struct keyset *next;                  /* Next active keyset in the list */
  unsigned ref;                         /* Reference count for keyset */
  struct peer *p;                       /* Pointer to peer structure */
  time_t t_exp;                         /* Expiry time for this keyset */
  unsigned long sz_exp, sz_regen;       /* Data limits for the keyset */
  T( unsigned seq; )                    /* Sequence number for tracing */
  unsigned f;                           /* Various useful flags */
  bulkctx *bulk;                        /* Bulk crypto transform */
  uint32 oseq;                          /* Outbound sequence number */
  seqwin iseq;                          /* Inbound sequence number */
};

#define KSF_LISTEN 1u                   /* Don't encrypt packets yet */
#define KSF_LINK 2u                     /* Key is in a linked list */

#define KSERR_REGEN -1                  /* Regenerate keys */
#define KSERR_NOKEYS -2                 /* No keys left */
#define KSERR_DECRYPT -3                /* Unable to decrypt message */
#define KSERR_SEQ -4                    /* Incorrect sequence number */
#define KSERR_MALFORMED -5              /* Input ciphertext is broken */

/* --- Key exchange --- *
 *
 * TrIPE uses the Wrestlers Protocol for its key exchange.  The Wrestlers
 * Protocol has a number of desirable features (e.g., perfect forward
 * secrecy, and zero-knowledge authentication) which make it attractive for
 * use in TrIPE.  The Wrestlers Protocol was designed by Mark Wooding and
 * Clive Jones.
 */

typedef struct retry {
  double t;                             /* Current retry time */
} retry;

#define KX_NCHAL 16u

typedef struct kxchal {
  struct keyexch *kx;                   /* Pointer back to key exchange */
  dhge *C;                              /* Responder's challenge */
  dhge *R;                              /* My reply to the challenge */
  keyset *ks;                           /* Pointer to temporary keyset */
  unsigned f;                           /* Various useful flags */
  sel_timer t;                          /* Response timer for challenge */
  retry rs;                             /* Retry state */
  octet hc[MAXHASHSZ];                  /* Hash of his challenge */
  octet ck[MAXHASHSZ];                  /* His magical check value */
  octet hswrq_in[MAXHASHSZ];            /* Inbound switch request message */
  octet hswok_in[MAXHASHSZ];            /* Inbound switch confirmation */
  octet hswrq_out[MAXHASHSZ];           /* Outbound switch request message */
  octet hswok_out[MAXHASHSZ];           /* Outbound switch confirmation */
} kxchal;

typedef struct keyexch {
  struct peer *p;                       /* Pointer back to the peer */
  kdata *kpriv;                         /* Private key and related info */
  kdata *kpub;                          /* Peer's public key */
  keyset **ks;                          /* Peer's list of keysets */
  unsigned f;                           /* Various useful flags */
  unsigned s;                           /* Current state in exchange */
  sel_timer t;                          /* Timer for next exchange */
  retry rs;                             /* Retry state */
  dhsc *a;                              /* My temporary secret */
  dhge *C;                              /* My challenge */
  dhge *RX;                             /* The expected response */
  unsigned nr;                          /* Number of extant responses */
  time_t t_valid;                       /* When this exchange goes bad */
  octet hc[MAXHASHSZ];                  /* Hash of my challenge */
  kxchal *r[KX_NCHAL];                  /* Array of challenges */
} keyexch;

#define KXF_TIMER 1u                    /* Waiting for a timer to go off */
#define KXF_DEAD 2u                     /* The key-exchanger isn't up */
#define KXF_PUBKEY 4u                   /* Key exchanger has a public key */
#define KXF_CORK 8u                     /* Don't send anything yet */

enum {
  KXS_DEAD,                             /* Uninitialized state (magical) */
  KXS_CHAL,                             /* Main answer-challenges state */
  KXS_COMMIT,                           /* Committed: send switch request */
  KXS_SWITCH                            /* Switched: send confirmation */
};

/* --- Tunnel structure --- *
 *
 * Used to maintain system-specific information about the tunnel interface.
 */

typedef struct tunnel tunnel;
struct peer;

typedef struct tunnel_ops {
  const char *name;                     /* Name of this tunnel driver */
  unsigned flags;                       /* Various interesting flags */
#define TUNF_PRIVOPEN 1u                /*   Need helper to open file */
  int (*init)(void);                    /* Initializes the system */
  tunnel *(*create)(struct peer */*p*/, int /*fd*/, char **/*ifn*/);
                                        /* Initializes a new tunnel */
  void (*setifname)(tunnel */*t*/, const char */*ifn*/);
                                        /*  Notifies ifname change */
  void (*inject)(tunnel */*t*/, buf */*b*/); /* Sends packet through if */
  void (*destroy)(tunnel */*t*/);       /* Destroys a tunnel */
} tunnel_ops;

#ifndef TUN_INTERNALS
struct tunnel { const tunnel_ops *ops; };
#endif

typedef struct tun_iter {
  const struct tunnel_node *next;
} tun_iter;

/* --- Peer statistics --- *
 *
 * Contains various interesting and not-so-interesting statistics about a
 * peer.  This is updated by various parts of the code.  The format of the
 * structure isn't considered private, and @p_stats@ returns a pointer to the
 * statistics block for a given peer.
 */

typedef struct stats {
  unsigned long sz_in, sz_out;          /* Size of all data in and out */
  unsigned long sz_kxin, sz_kxout;      /* Size of key exchange messages */
  unsigned long sz_ipin, sz_ipout;      /* Size of encapsulated IP packets */
  time_t t_start, t_last, t_kx;         /* Time peer created, last pk, kx */
  unsigned long n_reject;               /* Number of rejected packets */
  unsigned long n_in, n_out;            /* Number of packets in and out */
  unsigned long n_kxin, n_kxout;        /* Number of key exchange packets */
  unsigned long n_ipin, n_ipout;        /* Number of encrypted packets */
} stats;

/* --- Peer structure --- *
 *
 * The main structure which glues everything else together.
 */

typedef struct peerspec {
  char *name;                           /* Peer's name */
  char *privtag;                        /* Private key tag */
  char *tag;                            /* Public key tag */
  char *knock;                          /* Knock string, or null */
  const tunnel_ops *tops;               /* Tunnel operations */
  unsigned long t_ka;                   /* Keep alive interval */
  addr sa;                              /* Socket address to speak to */
  unsigned f;                           /* Flags for the peer */
#define PSF_KXMASK 255u                 /*   Key-exchange flags to set */
#define PSF_MOBILE 256u                 /*   Address may change rapidly */
#define PSF_EPHEM 512u                  /*   Association is ephemeral */
} peerspec;

typedef struct peer_byname {
  sym_base _b;
  struct peer *p;
} peer_byname;

typedef struct peer_byaddr {
  addrmap_base _b;
  struct peer *p;
} peer_byaddr;

typedef struct peer {
  peer_byname *byname;                  /* Lookup-by-name block */
  peer_byaddr *byaddr;                  /* Lookup-by-address block */
  struct ping *pings;                   /* Pings we're waiting for */
  peerspec spec;                        /* Specifications for this peer */
  int afix;                             /* Index of address family */
  tunnel *t;                            /* Tunnel for local packets */
  char *ifname;                         /* Interface name for tunnel */
  keyset *ks;                           /* List head for keysets */
  buf b;                                /* Buffer for sending packets */
  stats st;                             /* Statistics */
  keyexch kx;                           /* Key exchange protocol block */
  sel_timer tka;                        /* Timer for keepalives */
#define NWGT 16
  struct {
    octet msg[WGTLEN];                  /* Message prefix */
    unsigned sz;                        /* Length of prefix */
    time_t when;                        /* Time it was transmitted */
  } wgt[NWGT];                          /* Recently sent messages */
  unsigned wgtix;                       /* Next index to transmit */
} peer;

typedef struct peer_iter { sym_iter i; } peer_iter;

typedef struct udpsocket {
  sel_file sf;                          /* Selector for the socket */
  unsigned port;                        /* Chosen port number */
} udpsocket;

typedef struct ping {
  struct ping *next, *prev;             /* Links to next and previous */
  peer *p;                              /* Peer so we can free it */
  unsigned msg;                         /* Kind of response expected */
  uint32 id;                            /* Id so we can recognize response */
  octet magic[32];                      /* Some random data */
  sel_timer t;                          /* Timeout for ping */
  void (*func)(int /*rc*/, void */*arg*/); /* Function to call when done */
  void *arg;                            /* Argument for callback */
} ping;

enum {
  PING_NONOTIFY = -1,
  PING_OK = 0,
  PING_TIMEOUT,
  PING_PEERDIED,
  PING_MAX
};

/* --- Admin structure --- */

#define OBUFSZ 16384u

typedef struct obuf {
  struct obuf *next;                    /* Next buffer in list */
  char *p_in, *p_out;                   /* Pointers into the buffer */
  char buf[OBUFSZ];                     /* The actual buffer */
} obuf;

typedef struct oqueue {
  obuf *hd, *tl;                        /* Head and tail pointers */
} oqueue;

struct admin;

typedef struct admin_bgop {
  struct admin_bgop *next, *prev;       /* Links to next and previous */
  struct admin *a;                      /* Owner job */
  char *tag;                            /* Tag string for messages */
  void (*cancel)(struct admin_bgop *);  /* Destructor function */
} admin_bgop;

typedef struct admin_resop {
  admin_bgop bg;                        /* Background operation header */
  char *addr;                           /* Hostname to be resolved */
#ifdef HAVE_LIBADNS
  adns_query q;
#else
  bres_client r;                        /* Background resolver task */
#endif
  sel_timer t;                          /* Timer for resolver */
  addr sa;                              /* Socket address */
  unsigned port;                        /* Port number chosen */
  size_t sasz;                          /* Socket address size */
  void (*func)(struct admin_resop *, int); /* Handler */
} admin_resop;

enum { ARES_OK, ARES_FAIL };

typedef struct admin_addop {
  admin_resop r;                        /* Name resolution header */
  peerspec peer;                        /* Peer pending creation */
} admin_addop;

typedef struct admin_pingop {
  admin_bgop bg;                        /* Background operation header */
  ping ping;                            /* Ping pending response */
  struct timeval pingtime;              /* Time last ping was sent */
} admin_pingop;

typedef struct admin_service {
  sym_base _b;                          /* Hash table base structure */
  char *version;                        /* The provided version */
  struct admin *prov;                   /* Which client provides me */
  struct admin_service *next, *prev;    /* Client's list of services */
} admin_service;

typedef struct admin_svcop {
  admin_bgop bg;                        /* Background operation header */
  struct admin *prov;                   /* Client servicing this job */
  unsigned index;                       /* This job's index */
  struct admin_svcop *next, *prev;      /* Links for provider's jobs */
} admin_svcop;

typedef struct admin_jobentry {
  unsigned short seq;                   /* Zero if unused */
  union {
    admin_svcop *op;                    /* Operation, if slot in use, ... */
    uint32 next;                        /* ... or index of next free slot */
  } u;
} admin_jobentry;

typedef struct admin_jobtable {
  uint32 n, sz;                         /* Used slots and table size */
  admin_svcop *active;                  /* List of active jobs */
  uint32 free;                          /* Index of first free slot */
  admin_jobentry *v;                    /* And the big array of entries */
} admin_jobtable;

struct admin {
  struct admin *next, *prev;            /* Links to next and previous */
  unsigned f;                           /* Various useful flags */
  unsigned ref;                         /* Reference counter */
#ifndef NTRACE
  unsigned seq;                         /* Sequence number for tracing */
#endif
  oqueue out;                           /* Output buffer list */
  oqueue delay;                         /* Delayed output buffer list */
  admin_bgop *bg;                       /* Backgrounded operations */
  admin_service *svcs;                  /* Which services I provide */
  admin_jobtable j;                     /* Table of outstanding jobs */
  selbuf b;                             /* Line buffer for commands */
  sel_file w;                           /* Selector for write buffering */
};

#define AF_DEAD 1u                      /* Destroy this admin block */
#define AF_CLOSE 2u                     /* Client closed connection */
#define AF_NOTE 4u                      /* Catch notifications */
#define AF_WARN 8u                      /* Catch warning messages */
#ifndef NTRACE
#  define AF_TRACE 16u                  /* Catch tracing */
#endif
#define AF_FOREGROUND 32u               /* Quit server when client closes */

#ifndef NTRACE
#  define AF_ALLMSGS (AF_NOTE | AF_TRACE | AF_WARN)
#else
#  define AF_ALLMSGS (AF_NOTE | AF_WARN)
#endif

/*----- Global variables --------------------------------------------------*/

extern sel_state sel;                   /* Global I/O event state */
extern octet buf_i[PKBUFSZ], buf_o[PKBUFSZ], buf_t[PKBUFSZ], buf_u[PKBUFSZ];
extern udpsocket udpsock[NADDRFAM];     /* The master UDP sockets */
extern kdata *master;                   /* Default private key */
extern char *tag_priv;                  /* Default private key tag */

#ifndef NTRACE
extern const trace_opt tr_opts[];       /* Trace options array */
extern unsigned tr_flags;               /* Trace options flags */
#endif

/*----- Other macros ------------------------------------------------------*/

#define QUICKRAND                                                       \
  do { rand_quick(RAND_GLOBAL); noise_timer(RAND_GLOBAL); } while (0)

/*----- Key management ----------------------------------------------------*/

/* --- @km_init@ --- *
 *
 * Arguments:   @const char *privkr@ = private keyring file
 *              @const char *pubkr@ = public keyring file
 *              @const char *ptag@ = default private-key tag
 *
 * Returns:     Zero on success, @-1@ on failure.
 *
 * Use:         Initializes the key-management machinery, loading the
 *              keyrings and so on.
 */

extern int km_init(const char */*privkr*/, const char */*pubkr*/,
                   const char */*ptag*/);

/* --- @km_reload@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     Zero if OK, nonzero to force reloading of keys.
 *
 * Use:         Checks the keyrings to see if they need reloading.
 */

extern int km_reload(void);

/* --- @km_clear@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Forget the currently loaded keyrings.  The @master@ key will
 *              be cleared, but other keys already loaded will continue to
 *              exist until their reference count drops to zero.  Call
 *              @km_init@ to make everything work again.
 */

extern void km_clear(void);

/* --- @km_findpub@, @km_findpriv@ --- *
 *
 * Arguments:   @const char *tag@ = key tag to load
 *
 * Returns:     Pointer to the kdata object if successful, or null on error.
 *
 * Use:         Fetches a public or private key from the keyring.
 */

extern kdata *km_findpub(const char */*tag*/);
extern kdata *km_findpriv(const char */*tag*/);

/* --- @km_findpubbyid@, @km_findprivbyid@ --- *
 *
 * Arguments:   @uint32 id@ = key id to load
 *
 * Returns:     Pointer to the kdata object if successful, or null on error.
 *
 * Use:         Fetches a public or private key from the keyring given its
 *              numeric id.
 */

extern kdata *km_findpubbyid(uint32 /*id*/);
extern kdata *km_findprivbyid(uint32 /*id*/);

/* --- @km_samealgsp@ --- *
 *
 * Arguments:   @const kdata *kdx, *kdy@ = two key data objects
 *
 * Returns:     Nonzero if their two algorithm selections are the same.
 *
 * Use:         Checks sameness of algorithm selections: used to ensure that
 *              peers are using sensible algorithms.
 */

extern int km_samealgsp(const kdata */*kdx*/, const kdata */*kdy*/);

/* --- @km_ref@ --- *
 *
 * Arguments:   @kdata *kd@ = pointer to the kdata object
 *
 * Returns:     ---
 *
 * Use:         Claim a new reference to a kdata object.
 */

extern void km_ref(kdata */*kd*/);

/* --- @km_unref@ --- *
 *
 * Arguments:   @kdata *kd@ = pointer to the kdata object
 *
 * Returns:     ---
 *
 * Use:         Releases a reference to a kdata object.
 */

extern void km_unref(kdata */*kd*/);

/* --- @km_tag@ --- *
 *
 * Arguments:   @kdata *kd@ - pointer to the kdata object
 *
 * Returns:     A pointer to the short tag by which the kdata was loaded.
 */

extern const char *km_tag(kdata */*kd*/);

/*----- Key exchange ------------------------------------------------------*/

/* --- @kx_start@ --- *
 *
 * Arguments:   @keyexch *kx@ = pointer to key exchange context
 *              @int forcep@ = nonzero to ignore the quiet timer
 *
 * Returns:     ---
 *
 * Use:         Stimulates a key exchange.  If a key exchage is in progress,
 *              a new challenge is sent (unless the quiet timer forbids
 *              this); if no exchange is in progress, one is commenced.
 */

extern void kx_start(keyexch */*kx*/, int /*forcep*/);

/* --- @kx_message@ --- *
 *
 * Arguments:   @keyexch *kx@ = pointer to key exchange context
 *              @const addr *a@ = sender's IP address and port
 *              @unsigned msg@ = the message code
 *              @buf *b@ = pointer to buffer containing the packet
 *
 * Returns:     Nonzero if the sender's address was unknown.
 *
 * Use:         Reads a packet containing key exchange messages and handles
 *              it.
 */

extern int kx_message(keyexch */*kx*/, const addr */*a*/,
                      unsigned /*msg*/, buf */*b*/);

/* --- @kx_free@ --- *
 *
 * Arguments:   @keyexch *kx@ = pointer to key exchange context
 *
 * Returns:     ---
 *
 * Use:         Frees everything in a key exchange context.
 */

extern void kx_free(keyexch */*kx*/);

/* --- @kx_newkeys@ --- *
 *
 * Arguments:   @keyexch *kx@ = pointer to key exchange context
 *
 * Returns:     ---
 *
 * Use:         Informs the key exchange module that its keys may have
 *              changed.  If fetching the new keys fails, the peer will be
 *              destroyed, we log messages and struggle along with the old
 *              keys.
 */

extern void kx_newkeys(keyexch */*kx*/);

/* --- @kx_setup@ --- *
 *
 * Arguments:   @keyexch *kx@ = pointer to key exchange context
 *              @peer *p@ = pointer to peer context
 *              @keyset **ks@ = pointer to keyset list
 *              @unsigned f@ = various useful flags
 *
 * Returns:     Zero if OK, nonzero if it failed.
 *
 * Use:         Initializes a key exchange module.  The module currently
 *              contains no keys, and will attempt to initiate a key
 *              exchange.
 */

extern int kx_setup(keyexch */*kx*/, peer */*p*/,
                    keyset **/*ks*/, unsigned /*f*/);

/* --- @kx_init@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Initializes the key-exchange logic.
 */

extern void kx_init(void);

/*----- Keysets and symmetric cryptography --------------------------------*/

/* --- @ks_drop@ --- *
 *
 * Arguments:   @keyset *ks@ = pointer to a keyset
 *
 * Returns:     ---
 *
 * Use:         Decrements a keyset's reference counter.  If the counter hits
 *              zero, the keyset is freed.
 */

extern void ks_drop(keyset */*ks*/);

/* --- @ks_gen@ --- *
 *
 * Arguments:   @deriveargs *a@ = key derivation parameters (modified)
 *              @peer *p@ = pointer to peer information
 *
 * Returns:     A pointer to the new keyset.
 *
 * Use:         Derives a new keyset from the given key material.  This will
 *              set the @what@, @f@, and @hc@ members in @*a@; other members
 *              must be filled in by the caller.
 *
 *              The new key is marked so that it won't be selected for output
 *              by @ksl_encrypt@.  You can still encrypt data with it by
 *              calling @ks_encrypt@ directly.
 */

extern keyset *ks_gen(deriveargs */*a*/, peer */*p*/);

/* --- @ks_activate@ --- *
 *
 * Arguments:   @keyset *ks@ = pointer to a keyset
 *
 * Returns:     ---
 *
 * Use:         Activates a keyset, so that it can be used for encrypting
 *              outgoing messages.
 */

extern void ks_activate(keyset */*ks*/);

/* --- @ks_encrypt@ --- *
 *
 * Arguments:   @keyset *ks@ = pointer to a keyset
 *              @unsigned ty@ = message type
 *              @buf *b@ = pointer to input buffer
 *              @buf *bb@ = pointer to output buffer
 *
 * Returns:     Zero if successful; @KSERR_REGEN@ if we should negotiate a
 *              new key; @KSERR_NOKEYS@ if the key is not usable.  Also
 *              returns zero if there was insufficient buffer (but the output
 *              buffer is broken in this case).
 *
 * Use:         Encrypts a block of data using the key.  Note that the `key
 *              ought to be replaced' notification is only ever given once
 *              for each key.  Also note that this call forces a keyset to be
 *              used even if it's marked as not for data output.
 *
 *              The encryption transform is permitted to corrupt @buf_u@ for
 *              its own purposes.  Neither the source nor destination should
 *              be within @buf_u@; and callers mustn't expect anything stored
 *              in @buf_u@ to still
 */

extern int ks_encrypt(keyset */*ks*/, unsigned /*ty*/,
                      buf */*b*/, buf */*bb*/);

/* --- @ks_decrypt@ --- *
 *
 * Arguments:   @keyset *ks@ = pointer to a keyset
 *              @unsigned ty@ = expected type code
 *              @buf *b@ = pointer to an input buffer
 *              @buf *bb@ = pointer to an output buffer
 *
 * Returns:     Zero on success; @KSERR_DECRYPT@ on failure.  Also returns
 *              zero if there was insufficient buffer (but the output buffer
 *              is broken in this case).
 *
 * Use:         Attempts to decrypt a message using a given key.  Note that
 *              requesting decryption with a key directly won't clear a
 *              marking that it's not for encryption.
 *
 *              The decryption transform is permitted to corrupt @buf_u@ for
 *              its own purposes.  Neither the source nor destination should
 *              be within @buf_u@; and callers mustn't expect anything stored
 *              in @buf_u@ to still
 */

extern int ks_decrypt(keyset */*ks*/, unsigned /*ty*/,
                      buf */*b*/, buf */*bb*/);

/* --- @ksl_free@ --- *
 *
 * Arguments:   @keyset **ksroot@ = pointer to keyset list head
 *
 * Returns:     ---
 *
 * Use:         Frees (releases references to) all of the keys in a keyset.
 */

extern void ksl_free(keyset **/*ksroot*/);

/* --- @ksl_link@ --- *
 *
 * Arguments:   @keyset **ksroot@ = pointer to keyset list head
 *              @keyset *ks@ = pointer to a keyset
 *
 * Returns:     ---
 *
 * Use:         Links a keyset into a list.  A keyset can only be on one list
 *              at a time.  Bad things happen otherwise.
 */

extern void ksl_link(keyset **/*ksroot*/, keyset */*ks*/);

/* --- @ksl_prune@ --- *
 *
 * Arguments:   @keyset **ksroot@ = pointer to keyset list head
 *
 * Returns:     ---
 *
 * Use:         Prunes the keyset list by removing keys which mustn't be used
 *              any more.
 */

extern void ksl_prune(keyset **/*ksroot*/);

/* --- @ksl_encrypt@ --- *
 *
 * Arguments:   @keyset **ksroot@ = pointer to keyset list head
 *              @unsigned ty@ = message type
 *              @buf *b@ = pointer to input buffer
 *              @buf *bb@ = pointer to output buffer
 *
 * Returns:     Zero if successful; @KSERR_REGEN@ if it's time to negotiate a
 *              new key; @KSERR_NOKEYS@ if there are no suitable keys
 *              available.  Also returns zero if there was insufficient
 *              buffer space (but the output buffer is broken in this case).
 *
 * Use:         Encrypts a packet.
 */

extern int ksl_encrypt(keyset **/*ksroot*/, unsigned /*ty*/,
                       buf */*b*/, buf */*bb*/);

/* --- @ksl_decrypt@ --- *
 *
 * Arguments:   @keyset **ksroot@ = pointer to keyset list head
 *              @unsigned ty@ = expected type code
 *              @buf *b@ = pointer to input buffer
 *              @buf *bb@ = pointer to output buffer
 *
 * Returns:     Zero on success; @KSERR_DECRYPT@ on failure.  Also returns
 *              zero if there was insufficient buffer (but the output buffer
 *              is broken in this case).
 *
 * Use:         Decrypts a packet.
 */

extern int ksl_decrypt(keyset **/*ksroot*/, unsigned /*ty*/,
                       buf */*b*/, buf */*bb*/);

/*----- Challenges --------------------------------------------------------*/

/* --- @c_new@ --- *
 *
 * Arguments:   @const void *m@ = pointer to associated message, or null
 *              @size_t msz@ = length of associated message
 *              @buf *b@ = where to put the challenge
 *
 * Returns:     Zero if OK, nonzero on error.
 *
 * Use:         Issues a new challenge.
 */

extern int c_new(const void */*m*/, size_t /*msz*/, buf */*b*/);

/* --- @c_check@ --- *
 *
 * Arguments:   @const void *m@ = pointer to associated message, or null
 *              @size_t msz@ = length of associated message
 *              @buf *b@ = where to find the challenge
 *
 * Returns:     Zero if OK, nonzero if it didn't work.
 *
 * Use:         Checks a challenge.  On failure, the buffer is broken.
 */

extern int c_check(const void */*m*/, size_t /*msz*/, buf */*b*/);

/*----- Administration interface ------------------------------------------*/

#define A_END ((char *)0)

/* --- @a_vformat@ --- *
 *
 * Arguments:   @dstr *d@ = where to leave the formatted message
 *              @const char *fmt@ = pointer to format string
 *              @va_list *ap@ = arguments in list
 *
 * Returns:     ---
 *
 * Use:         Main message token formatting driver.  The arguments are
 *              interleaved formatting tokens and their parameters, finally
 *              terminated by an entry @A_END@.
 *
 *              Tokens recognized:
 *
 *                * "*..." ... -- pretokenized @dstr_putf@-like string
 *
 *                * "?ADDR" SOCKADDR -- a socket address, to be converted
 *
 *                * "?B64" BUFFER SIZE -- binary data to be base64-encoded
 *
 *                * "?TOKENS" VECTOR -- null-terminated vector of tokens
 *
 *                * "?PEER" PEER -- peer's name
 *
 *                * "?ERR" CODE -- system error code
 *
 *                * "?ERRNO" -- system error code from @errno@
 *
 *                * "[!]..." ... -- @dstr_putf@-like string as single token
 */

extern void a_vformat(dstr */*d*/, const char */*fmt*/, va_list */*ap*/);

/* --- @a_format@ --- *
 *
 * Arguments:   @dstr *d@ = where to leave the formatted message
 *              @const char *fmt@ = pointer to format string
 *
 * Returns:     ---
 *
 * Use:         Writes a tokenized message into a string, for later
 *              presentation.
 */

extern void EXECL_LIKE(0) a_format(dstr */*d*/, const char */*fmt*/, ...);

/* --- @a_info@ --- *
 *
 * Arguments:   @admin *a@ = connection
 *              @const char *fmt@ = format string
 *              @...@ = other arguments
 *
 * Returns:     ---
 *
 * Use:         Report information to an admin client.
 */

extern void EXECL_LIKE(0) a_info(admin */*a*/, const char */*fmt*/, ...);

/* --- @a_warn@ --- *
 *
 * Arguments:   @const char *fmt@ = pointer to format string
 *              @...@ = other arguments
 *
 * Returns:     ---
 *
 * Use:         Informs all admin connections of a warning.
 */

extern void EXECL_LIKE(0) a_warn(const char */*fmt*/, ...);

/* --- @a_notify@ --- *
 *
 * Arguments:   @const char *fmt@ = pointer to format string
 *              @...@ = other arguments
 *
 * Returns:     ---
 *
 * Use:         Sends a notification to interested admin connections.
 */

extern void EXECL_LIKE(0) a_notify(const char */*fmt*/, ...);

/* --- @a_create@ --- *
 *
 * Arguments:   @int fd_in, fd_out@ = file descriptors to use
 *              @unsigned f@ = initial flags to set
 *
 * Returns:     ---
 *
 * Use:         Creates a new admin connection.  It's safe to call this
 *              before @a_init@ -- and, indeed, this makes sense if you also
 *              call @a_switcherr@ to report initialization errors through
 *              the administration machinery.
 */

extern void a_create(int /*fd_in*/, int /*fd_out*/, unsigned /*f*/);

/* --- @a_preselect@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Informs the admin module that we're about to select again,
 *              and that it should do cleanup things it has delayed until a
 *              `safe' time.
 */

extern void a_preselect(void);

/* --- @a_daemon@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Informs the admin module that it's a daemon.
 */

extern void a_daemon(void);

/* --- @a_listen@ --- *
 *
 * Arguments:   @const char *name@ = socket name to create
 *              @uid_t u@ = user to own the socket
 *              @gid_t g@ = group to own the socket
 *              @mode_t m@ = permissions to set on the socket
 *
 * Returns:     Zero on success, @-1@ on failure.
 *
 * Use:         Creates the admin listening socket.
 */

extern int a_listen(const char */*sock*/,
                    uid_t /*u*/, gid_t /*g*/, mode_t /*m*/);

/* --- @a_unlisten@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Stops listening to the administration socket and removes it.
 */

extern void a_unlisten(void);

/* --- @a_switcherr@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Arrange to report warnings, trace messages, etc. to
 *              administration clients rather than the standard-error stream.
 *
 *              Obviously this makes no sense unless there is at least one
 *              client established.  Calling @a_listen@ won't help with this,
 *              because the earliest a new client can connect is during the
 *              first select-loop iteration, which is too late: some initial
 *              client must have been added manually using @a_create@.
 */

extern void a_switcherr(void);

/* --- @a_signals@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Establishes handlers for the obvious signals.
 */

extern void a_signals(void);

/* --- @a_init@ --- *
 *
 * Arguments:   @const char *sock@ = socket name to create
 *              @uid_t u@ = user to own the socket
 *              @gid_t g@ = group to own the socket
 *              @mode_t m@ = permissions to set on the socket
 *
 * Returns:     Zero on success, @-1@ on failure.
 *
 * Use:         Creates the admin listening socket.
 */

extern int a_init(void);

/*----- Mapping with addresses as keys ------------------------------------*/

/* --- @am_create@ --- *
 *
 * Arguments:   @addrmap *m@ = pointer to map
 *
 * Returns:     ---
 *
 * Use:         Create an address map, properly set up.
 */

extern void am_create(addrmap */*m*/);

/* --- @am_destroy@ --- *
 *
 * Arguments:   @addrmap *m@ = pointer to map
 *
 * Returns:     ---
 *
 * Use:         Destroy an address map, throwing away all the entries.
 */

extern void am_destroy(addrmap */*m*/);

/* --- @am_find@ --- *
 *
 * Arguments:   @addrmap *m@ = pointer to map
 *              @const addr *a@ = address to look up
 *              @size_t sz@ = size of block to allocate
 *              @unsigned *f@ = where to store flags
 *
 * Returns:     Pointer to found item, or null.
 *
 * Use:         Finds a record with the given IP address, set @*f@ nonzero
 *              and returns it.  If @sz@ is zero, and no match was found,
 *              return null; otherwise allocate a new block of @sz@ bytes,
 *              clear @*f@ to zero and return the block pointer.
 */

extern void *am_find(addrmap */*m*/, const addr */*a*/,
                     size_t /*sz*/, unsigned */*f*/);

/* --- @am_remove@ --- *
 *
 * Arguments:   @addrmap *m@ = pointer to map
 *              @void *i@ = pointer to the item
 *
 * Returns:     ---
 *
 * Use:         Removes an item from the map.
 */

extern void am_remove(addrmap */*m*/, void */*i*/);

/*----- Privilege separation ----------------------------------------------*/

/* --- @ps_trace@ --- *
 *
 * Arguments:   @unsigned mask@ = trace mask to check
 *              @const char *fmt@ = message format
 *              @...@ = values for placeholders
 *
 * Returns:     ---
 *
 * Use:         Writes a trace message.
 */

T( extern void PRINTF_LIKE(2, 3)
     ps_trace(unsigned /*mask*/, const char */*fmt*/, ...); )

/* --- @ps_warn@ --- *
 *
 * Arguments:   @const char *fmt@ = message format
 *              @...@ = values for placeholders
 *
 * Returns:     ---
 *
 * Use:         Writes a warning message.
 */

extern void PRINTF_LIKE(1, 2) ps_warn(const char */*fmt*/, ...);

/* --- @ps_tunfd@ --- *
 *
 * Arguments:   @const tunnel_ops *tops@ = pointer to tunnel operations
 *              @char **ifn@ = where to put the interface name
 *
 * Returns:     The file descriptor, or @-1@ on error.
 *
 * Use:         Fetches a file descriptor for a tunnel driver.
 */

extern int ps_tunfd(const tunnel_ops */*tops*/, char **/*ifn*/);

/* --- @ps_split@ --- *
 *
 * Arguments:   @int detachp@ = whether to detach the child from its terminal
 *
 * Returns:     Zero on success, @-1@ on failure.
 *
 * Use:         Separates off the privileged tunnel-opening service from the
 *              rest of the server.
 */

extern int ps_split(int /*detachp*/);

/* --- @ps_quit@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Detaches from the helper process.
 */

extern void ps_quit(void);

/*----- Peer management ---------------------------------------------------*/

/* --- @p_updateaddr@ --- *
 *
 * Arguments:   @peer *p@ = pointer to peer block
 *              @const addr *a@ = address to associate with this peer
 *
 * Returns:     Zero if the address was changed; @+1@ if it was already
 *              right.
 *
 * Use:         Updates our idea of @p@'s address.
 */

extern int p_updateaddr(peer */*p*/, const addr */*a*/);

/* --- @p_txstart@ --- *
 *
 * Arguments:   @peer *p@ = pointer to peer block
 *              @unsigned msg@ = message type code
 *
 * Returns:     A pointer to a buffer to write to.
 *
 * Use:         Starts sending to a peer.  Only one send can happen at a
 *              time.
 */

extern buf *p_txstart(peer */*p*/, unsigned /*msg*/);

/* --- @p_txaddr@ --- *
 *
 * Arguments:   @const addr *a@ = recipient address
 *              @const void *p@ = pointer to packet to send
 *              @size_t sz@ = length of packet
 *
 * Returns:     Zero if successful, nonzero on error.
 *
 * Use:         Sends a packet to an address which (possibly) isn't a current
 *              peer.
 */

extern int p_txaddr(const addr */*a*/, const void */*p*/, size_t /*sz*/);

/* --- @p_txend@ --- *
 *
 * Arguments:   @peer *p@ = pointer to peer block
 *              @unsigned f@ = flags
 *
 * Returns:     ---
 *
 * Use:         Sends a packet to the peer.
 */

#define TXF_WGT 1u                      /* Include in who-goes-there table */
extern void p_txend(peer */*p*/, unsigned /*f*/);

/* --- @p_pingsend@ --- *
 *
 * Arguments:   @peer *p@ = destination peer
 *              @ping *pg@ = structure to fill in
 *              @unsigned type@ = message type
 *              @unsigned long timeout@ = how long to wait before giving up
 *              @void (*func)(int, void *)@ = callback function
 *              @void *arg@ = argument for callback
 *
 * Returns:     Zero if successful, nonzero if it failed.
 *
 * Use:         Sends a ping to a peer.  Call @func@ with a nonzero argument
 *              if we get an answer within the timeout, or zero if no answer.
 */

extern int p_pingsend(peer */*p*/, ping */*pg*/, unsigned /*type*/,
                      unsigned long /*timeout*/,
                      void (*/*func*/)(int, void *), void */*arg*/);

/* --- @p_pingdone@ --- *
 *
 * Arguments:   @ping *p@ = ping structure
 *              @int rc@ = return code to pass on
 *
 * Returns:     ---
 *
 * Use:         Disposes of a ping structure, maybe sending a notification.
 */

extern void p_pingdone(ping */*p*/, int /*rc*/);

/* --- @p_greet@ --- *
 *
 * Arguments:   @peer *p@ = peer to send to
 *              @const void *c@ = pointer to challenge
 *              @size_t sz@ = size of challenge
 *
 * Returns:     ---
 *
 * Use:         Sends a greeting packet.
 */

extern void p_greet(peer */*p*/, const void */*c*/, size_t /*sz*/);

/* --- @p_tun@ --- *
 *
 * Arguments:   @peer *p@ = pointer to peer block
 *              @buf *b@ = buffer containing incoming packet
 *
 * Returns:     ---
 *
 * Use:         Handles a packet which needs to be sent to a peer.
 */

extern void p_tun(peer */*p*/, buf */*b*/);

/* --- @p_keyreload@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Forces a check of the daemon's keyring files.
 */

extern void p_keyreload(void);

/* --- @p_interval@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Called periodically to do tidying.
 */

extern void p_interval(void);

/* --- @p_stats@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's statistics.
 */

extern stats *p_stats(peer */*p*/);

/* --- @p_ifname@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's interface name.
 */

extern const char *p_ifname(peer */*p*/);

/* --- @p_setifname@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *              @const char *name@ = pointer to the new name
 *
 * Returns:     ---
 *
 * Use:         Changes the name held for a peer's interface.
 */

extern void p_setifname(peer */*p*/, const char */*name*/);

/* --- @p_addr@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's address.
 */

extern const addr *p_addr(peer */*p*/);

/* --- @p_bind@ --- *
 *
 * Arguments:   @struct addrinfo *ailist@ = addresses to bind to
 *
 * Returns:     Zero on success, @-1@ on failure.
 *
 * Use:         Binds to the main UDP sockets.
 */

extern int p_bind(struct addrinfo */*ailist*/);

/* --- @p_unbind@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Unbinds the UDP sockets.  There must not be any active peers,
 *              and none can be created until the sockets are rebound.
 */

extern void p_unbind(void);

/* --- @p_init@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Initializes the peer system.
 */

extern void p_init(void);

/* --- @p_addtun@ --- *
 *
 * Arguments:   @const tunnel_ops *tops@ = tunnel ops to add
 *
 * Returns:     Zero on success, @-1@ on failure.
 *
 * Use:         Adds a tunnel class to the list of known classes, if it
 *              initializes properly.  If there is no current default tunnel,
 *              then this one is made the default.
 *
 *              Does nothing if the tunnel class is already known.  So adding
 *              a bunch of tunnels takes quadratic time, but there will be
 *              too few to care about.
 */

extern int p_addtun(const tunnel_ops */*tops*/);

/* --- @p_setdflttun@ --- *
 *
 * Arguments:   @const tunnel_ops *tops@ = tunnel ops to set
 *
 * Returns:     ---
 *
 * Use:         Sets the default tunnel.  It must already be registered.  The
 *              old default is forgotten.
 */

extern void p_setdflttun(const tunnel_ops */*tops*/);

/* --- @p_dflttun@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     A pointer to the current default tunnel operations, or null
 *              if no tunnels are defined.
 */

extern const tunnel_ops *p_dflttun(void);

/* --- @p_findtun@ --- *
 *
 * Arguments:   @const char *name@ = tunnel name
 *
 * Returns:     Pointer to the tunnel operations, or null.
 *
 * Use:         Finds the operations for a named tunnel class.
 */

extern const tunnel_ops *p_findtun(const char */*name*/);

/* --- @p_mktuniter@ --- *
 *
 * Arguments:   @tuniter *i@ = pointer to iterator to initialize
 *
 * Returns:     ---
 *
 * Use:         Initializes a tunnel iterator.
 */

extern void p_mktuniter(tun_iter */*i*/);

/* --- @p_nexttun@ --- *
 *
 * Arguments:   @tuniter *i@ = pointer to iterator
 *
 * Returns:     Pointer to the next tunnel's operations, or null.
 */

extern const tunnel_ops *p_nexttun(tun_iter */*i*/);

/* --- @FOREACH_TUN@ --- *
 *
 * Arguments:   @tops@ = name to bind to each tunnel
 *              @stuff@ = thing to do for each item
 *
 * Use:         Does something for each known tunnel class.
 */

#define FOREACH_TUN(tops, stuff) do {                                   \
  tun_iter i_;                                                          \
  const tunnel_ops *tops;                                               \
  for (p_mktuniter(&i_); (tops = p_nexttun(&i_)) != 0; ) stuff;         \
} while (0)

/* --- @p_create@ --- *
 *
 * Arguments:   @peerspec *spec@ = information about this peer
 *
 * Returns:     Pointer to the peer block, or null if it failed.
 *
 * Use:         Creates a new named peer block.  No peer is actually attached
 *              by this point.
 */

extern peer *p_create(peerspec */*spec*/);

/* --- @p_name@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's name.
 *
 * Use:         Equivalent to @p_spec(p)->name@.
 */

extern const char *p_name(peer */*p*/);

/* --- @p_tag@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's public key tag.
 */

extern const char *p_tag(peer */*p*/);

/* --- @p_privtag@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's private key tag.
 */

extern const char *p_privtag(peer */*p*/);

/* --- @p_spec@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     Pointer to the peer's specification
 */

extern const peerspec *p_spec(peer */*p*/);

/* --- @p_findbyaddr@ --- *
 *
 * Arguments:   @const addr *a@ = address to look up
 *
 * Returns:     Pointer to the peer block, or null if not found.
 *
 * Use:         Finds a peer by address.
 */

extern peer *p_findbyaddr(const addr */*a*/);

/* --- @p_find@ --- *
 *
 * Arguments:   @const char *name@ = name to look up
 *
 * Returns:     Pointer to the peer block, or null if not found.
 *
 * Use:         Finds a peer by name.
 */

extern peer *p_find(const char */*name*/);

/* --- @p_destroy@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer
 *              @int bye@ = say goodbye to the peer?
 *
 * Returns:     ---
 *
 * Use:         Destroys a peer.
 */

extern void p_destroy(peer */*p*/, int /*bye*/);

/* --- @p_destroyall@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Destroys all of the peers, saying goodbye.
 */

extern void p_destroyall(void);

/* --- @FOREACH_PEER@ --- *
 *
 * Arguments:   @p@ = name to bind to each peer
 *              @stuff@ = thing to do for each item
 *
 * Use:         Does something for each current peer.
 */

#define FOREACH_PEER(p, stuff) do {                                     \
  peer_iter i_;                                                         \
  peer *p;                                                              \
  for (p_mkiter(&i_); (p = p_next(&i_)) != 0; ) stuff                   \
} while (0)

/* --- @p_mkiter@ --- *
 *
 * Arguments:   @peer_iter *i@ = pointer to an iterator
 *
 * Returns:     ---
 *
 * Use:         Initializes the iterator.
 */

extern void p_mkiter(peer_iter */*i*/);

/* --- @p_next@ --- *
 *
 * Arguments:   @peer_iter *i@ = pointer to an iterator
 *
 * Returns:     Next peer, or null if at the end.
 *
 * Use:         Returns the next peer.
 */

extern peer *p_next(peer_iter */*i*/);

/*----- The interval timer ------------------------------------------------*/

/* --- @iv_addreason@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Adds an `interval timer reason'; if there are no others, the
 *              interval timer is engaged.
 */

extern void iv_addreason(void);

/* --- @iv_rmreason@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Removes an interval timer reason; if there are none left, the
 *              interval timer is disengaged.
 */

extern void iv_rmreason(void);

/*----- The main loop -----------------------------------------------------*/

/* --- @lp_init@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Initializes the main loop.  Most importantly, this sets up
 *              the select multiplexor that everything else hooks onto.
 */

extern void lp_init(void);

/* --- @lp_end@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Requests an exit from the main loop.
 */

extern void lp_end(void);

/* --- @lp_run@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     Zero on successful termination; @-1@ if things went wrong.
 *
 * Use:         Cranks the main loop until it should be cranked no more.
 */

extern int lp_run(void);

/*----- Tunnel drivers ----------------------------------------------------*/

#ifdef TUN_LINUX
  extern const tunnel_ops tun_linux;
#endif

#ifdef TUN_UNET
  extern const tunnel_ops tun_unet;
#endif

#ifdef TUN_BSD
  extern const tunnel_ops tun_bsd;
#endif

extern const tunnel_ops tun_slip;

/*----- Other handy utilities ---------------------------------------------*/

/* --- @timestr@ --- *
 *
 * Arguments:   @time_t t@ = a time to convert
 *
 * Returns:     A pointer to a textual representation of the time.
 *
 * Use:         Converts a time to a textual representation.  Corrupts
 *              @buf_u@.
 */

extern const char *timestr(time_t /*t*/);

/* --- @mystrieq@ --- *
 *
 * Arguments:   @const char *x, *y@ = two strings
 *
 * Returns:     True if @x@ and @y are equal, up to case.
 */

extern int mystrieq(const char */*x*/, const char */*y*/);

/* --- @afix@ --- *
 *
 * Arguments:   @int af@ = an address family code
 *
 * Returns:     The index of the address family's record in @aftab@, or @-1@.
 */

extern int afix(int af);

/* --- @addrsz@ --- *
 *
 * Arguments:   @const addr *a@ = a network address
 *
 * Returns:     The size of the address, for passing into the sockets API.
 */

extern socklen_t addrsz(const addr */*a*/);

/* --- @getport@, @setport@ --- *
 *
 * Arguments:   @addr *a@ = a network address
 *              @unsigned port@ = port number to set
 *
 * Returns:     ---
 *
 * Use:         Retrieves or sets the port number in an address structure.
 */

extern unsigned getport(addr */*a*/);
extern void setport(addr */*a*/, unsigned /*port*/);

/* --- @seq_reset@ --- *
 *
 * Arguments:   @seqwin *s@ = sequence-checking window
 *
 * Returns:     ---
 *
 * Use:         Resets a sequence number window.
 */

extern void seq_reset(seqwin */*s*/);

/* --- @seq_check@ --- *
 *
 * Arguments:   @seqwin *s@ = sequence-checking window
 *              @uint32 q@ = sequence number to check
 *              @const char *service@ = service to report message from
 *
 * Returns:     A @SEQ_@ code.
 *
 * Use:         Checks a sequence number against the window, updating things
 *              as necessary.
 */

extern int seq_check(seqwin */*s*/, uint32 /*q*/, const char */*service*/);

typedef struct ratelim {
  unsigned n, max, persec;
  struct timeval when;
} ratelim;

/* --- @ratelim_init@ --- *
 *
 * Arguments:   @ratelim *r@ = rate-limiting state to fill in
 *              @unsigned persec@ = credit to accumulate per second
 *              @unsigned max@ = maximum credit to retain
 *
 * Returns:     ---
 *
 * Use:         Initialize a rate-limiting state.
 */

extern void ratelim_init(ratelim */*r*/,
                         unsigned /*persec*/, unsigned /*max*/);

/* --- @ratelim_withdraw@ --- *
 *
 * Arguments:   @ratelim *r@ = rate-limiting state
 *              @unsigned n@ = credit to withdraw
 *
 * Returns:     Zero if successful; @-1@ if there is unsufficient credit
 *
 * Use:         Updates the state with any accumulated credit.  Then, if
 *              there there are more than @n@ credits available, withdraw @n@
 *              and return successfully; otherwise, report failure.
 */

extern int ratelim_withdraw(ratelim */*r*/, unsigned /*n*/);

/* --- @ies_encrypt@ --- *
 *
 * Arguments:   @kdata *kpub@ = recipient's public key
 *              @unsigned ty@ = message type octet
 *              @buf *b@ = input message buffer
 *              @buf *bb@ = output buffer for the ciphertext
 *
 * Returns:     On error, returns a @KSERR_...@ code or breaks the buffer;
 *              on success, returns zero and the buffer is good.
 *
 * Use:         Encrypts a message for a recipient, given their public key.
 *              This does not (by itself) provide forward secrecy or sender
 *              authenticity.  The ciphertext is self-delimiting (unlike
 *              @ks_encrypt@).
 */

extern int ies_encrypt(kdata */*kpub*/, unsigned /*ty*/,
                       buf */*b*/, buf */*bb*/);

/* --- @ies_decrypt@ --- *
 *
 * Arguments:   @kdata *kpub@ = private key key
 *              @unsigned ty@ = message type octet
 *              @buf *b@ = input ciphertext buffer
 *              @buf *bb@ = output buffer for the message
 *
 * Returns:     On error, returns a @KSERR_...@ code; on success, returns
 *              zero and the buffer is good.
 *
 * Use:         Decrypts a message encrypted using @ies_encrypt@, given our
 *              private key.
 */

extern int ies_decrypt(kdata */*kpriv*/, unsigned /*ty*/,
                       buf */*b*/, buf */*bb*/);

/*----- That's all, folks -------------------------------------------------*/

#ifdef __cplusplus
  }
#endif

#endif