mdw@git.distorted.org.uk Git - secnet/blob - udp.c

   1 /* UDP send/receive module for secnet */
   2
   3 /* This module enables sites to communicate by sending UDP
   4  * packets. When an instance of the module is created we can
   5  * optionally bind to a particular local IP address (not implemented
   6  * yet).
   7  *
   8  * Sites register an interest in local port numbers for receiving
   9  * packets, and can also send packets. We don't care about the source
  10  * port number for sending packets.
  11  *
  12  * Packets are offered to registered receivers in turn. Once one
  13  * accepts it, it isn't offered to any more. */
  14
  15 #include "secnet.h"
  16 #include <stdio.h>
  17 #include <unistd.h>
  18 #include <fcntl.h>
  19 #include <string.h>
  20 #include <errno.h>
  21 #include <sys/socket.h>
  22 #include <sys/wait.h>
  23 #include "util.h"
  24 #include "unaligned.h"
  25
  26 static beforepoll_fn udp_beforepoll;
  27 static afterpoll_fn udp_afterpoll;
  28 static comm_request_notify_fn request_notify;
  29 static comm_release_notify_fn release_notify;
  30 static comm_sendmsg_fn udp_sendmsg;
  31
  32 /* The UDP module exports a pure closure which can be used to construct a
  33  * UDP send/receive module. Arguments:
  34  */
  35
  36 struct notify_list {
  37     comm_notify_fn *fn;
  38     void *state;
  39     struct notify_list *next;
  40 };
  41
  42 struct udp {
  43     closure_t cl;
  44     struct comm_if ops;
  45     struct cloc loc;
  46     uint16_t port;
  47     int fd;
  48     string_t authbind;
  49     struct buffer_if *rbuf;
  50     struct notify_list *notify;
  51 };
  52
  53 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  54                           int *timeout_io, const struct timeval *tv,
  55                           uint64_t *now)
  56 {
  57     struct udp *st=state;
  58     if (*nfds_io<1) {
  59         *nfds_io=1;
  60         return ERANGE;
  61     }
  62     *nfds_io=1;
  63     fds->fd=st->fd;
  64     fds->events=POLLIN;
  65     return 0;
  66 }
  67
  68 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
  69                           const struct timeval *tv, uint64_t *now)
  70 {
  71     struct udp *st=state;
  72     struct sockaddr_in from;
  73     int fromlen;
  74     struct notify_list *n;
  75     bool_t done;
  76     int rv;
  77
  78     if (nfds && (fds->revents & POLLIN)) {
  79         do {
  80             fromlen=sizeof(from);
  81             BUF_ASSERT_FREE(st->rbuf);
  82             BUF_ALLOC(st->rbuf,"udp_afterpoll");
  83             rv=recvfrom(st->fd, st->rbuf->start, st->rbuf->len, 0,
  84                         (struct sockaddr *)&from, &fromlen);
  85             if (rv>0) {
  86                 st->rbuf->size=rv;
  87                 done=False;
  88                 for (n=st->notify; n; n=n->next) {
  89                     if (n->fn(n->state, st->rbuf, &from)) {
  90                         done=True;
  91                         break;
  92                     }
  93                 }
  94                 if (!done) {
  95                     uint32_t source,dest;
  96                     /* XXX manufacture and send NAK packet */
  97                     source=get_uint32(st->rbuf->start); /* Us */
  98                     dest=get_uint32(st->rbuf->start+4); /* Them */
  99                     Message(M_INFO,"udp (port %d): sending NAK\n",st->port);
 100                     buffer_init(st->rbuf,0);
 101                     buf_append_uint32(st->rbuf,dest);
 102                     buf_append_uint32(st->rbuf,source);
 103                     buf_append_uint32(st->rbuf,0); /* NAK is msg type 0 */
 104                     sendto(st->fd, st->rbuf->start, st->rbuf->size, 0,
 105                            (struct sockaddr *)&from, sizeof(from));
 106                     BUF_FREE(st->rbuf);
 107                 }
 108                 BUF_ASSERT_FREE(st->rbuf);
 109             } else {
 110                 BUF_FREE(st->rbuf);
 111             }
 112         } while (rv>=0);
 113     }
 114 }
 115
 116 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 117 {
 118     struct udp *st=commst;
 119     struct notify_list *n;
 120
 121     n=safe_malloc(sizeof(*n),"request_notify");
 122     n->fn=fn;
 123     n->state=nst;
 124     n->next=st->notify;
 125     st->notify=n;
 126 }
 127
 128 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 129 {
 130     struct udp *st=commst;
 131     struct notify_list *n, **p, *t;
 132
 133     /* XXX untested */
 134     p=&st->notify;
 135     for (n=st->notify; n; )
 136     {
 137         if (n->state==nst && n->fn==fn) {
 138             t=n;
 139             *p=n->next;
 140             n=n->next;
 141             free(t);
 142         } else {
 143             p=&n->next;
 144             n=n->next;
 145         }
 146     }
 147 }
 148
 149 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 150                           struct sockaddr_in *dest)
 151 {
 152     struct udp *st=commst;
 153
 154     /* XXX fix error reporting */
 155     sendto(st->fd, buf->start, buf->size, 0,
 156            (struct sockaddr *)dest, sizeof(*dest));
 157
 158     return True;
 159 }
 160
 161 static void udp_phase_hook(void *sst, uint32_t new_phase)
 162 {
 163     struct udp *st=sst;
 164     struct sockaddr_in addr;
 165
 166     st->fd=socket(AF_INET, SOCK_DGRAM, 0);
 167     if (st->fd<0) {
 168         fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line);
 169     }
 170     if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) {
 171         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 172                      st->loc.file,st->loc.line);
 173     }
 174     if (fcntl(st->fd, F_SETFD, FD_CLOEXEC)==-1) {
 175         fatal_perror("udp (%s:%d): fcntl(set FD_CLOEXEC)",
 176                      st->loc.file,st->loc.line);
 177     }
 178
 179     memset(&addr, 0, sizeof(addr));
 180     addr.sin_family=AF_INET;
 181     addr.sin_port=htons(st->port);
 182     if (st->authbind) {
 183         pid_t c;
 184         int status;
 185
 186         /* XXX this fork() and waitpid() business needs to be hidden
 187            in some system-specific library functions. */
 188         c=fork();
 189         if (c==-1) {
 190             fatal_perror("udp_phase_hook: fork() for authbind");
 191         }
 192         if (c==0) {
 193             char *argv[4];
 194             argv[0]=st->authbind;
 195             argv[1]="00000000";
 196             argv[2]=alloca(8);
 197             if (!argv[2]) exit(ENOMEM);
 198             sprintf(argv[2],"%04X",htons(st->port));
 199             argv[3]=NULL;
 200             dup2(st->fd,0);
 201             execvp(st->authbind,argv);
 202             exit(ENOEXEC);
 203         }
 204         waitpid(c,&status,0);
 205         if (WEXITSTATUS(status)!=0) {
 206             errno=WEXITSTATUS(status);
 207             fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
 208         }
 209     } else {
 210         if (bind(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) {
 211             fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
 212         }
 213     }
 214
 215     register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp");
 216 }
 217
 218 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 219                          list_t *args)
 220 {
 221     struct udp *st;
 222     item_t *i;
 223     dict_t *d;
 224
 225     st=safe_malloc(sizeof(*st),"udp_apply(st)");
 226     st->loc=loc;
 227     st->cl.description="udp";
 228     st->cl.type=CL_COMM;
 229     st->cl.apply=NULL;
 230     st->cl.interface=&st->ops;
 231     st->ops.st=st;
 232     st->ops.request_notify=request_notify;
 233     st->ops.release_notify=release_notify;
 234     st->ops.sendmsg=udp_sendmsg;
 235     st->port=0;
 236
 237     i=list_elem(args,0);
 238     if (!i || i->type!=t_dict) {
 239         cfgfatal(st->loc,"udp","first argument must be a dictionary\n");
 240     }
 241     d=i->data.dict;
 242
 243     st->port=dict_read_number(d,"port",True,"udp",st->loc,0);
 244     st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
 245     st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
 246
 247     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 248
 249     return new_closure(&st->cl);
 250 }
 251
 252 init_module udp_module;
 253 void udp_module(dict_t *dict)
 254 {
 255     add_closure(dict,"udp",udp_apply);
 256 }