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
  25 static beforepoll_fn udp_beforepoll;
  26 static afterpoll_fn udp_afterpoll;
  27 static comm_request_notify_fn request_notify;
  28 static comm_release_notify_fn release_notify;
  29 static comm_sendmsg_fn udp_sendmsg;
  30
  31 /* The UDP module exports a pure closure which can be used to construct a
  32  * UDP send/receive module. Arguments:
  33  */
  34
  35 struct notify_list {
  36     comm_notify_fn *fn;
  37     void *state;
  38     struct notify_list *next;
  39 };
  40
  41 struct udp {
  42     closure_t cl;
  43     struct comm_if ops;
  44     struct cloc loc;
  45     uint16_t port;
  46     int fd;
  47     string_t authbind;
  48     struct buffer_if *rbuf;
  49     struct notify_list *notify;
  50 };
  51
  52 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  53                           int *timeout_io, const struct timeval *tv,
  54                           uint64_t *now)
  55 {
  56     struct udp *st=state;
  57     if (*nfds_io<1) {
  58         *nfds_io=1;
  59         return ERANGE;
  60     }
  61     *nfds_io=1;
  62     fds->fd=st->fd;
  63     fds->events=POLLIN;
  64     return 0;
  65 }
  66
  67 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
  68                           const struct timeval *tv, uint64_t *now)
  69 {
  70     struct udp *st=state;
  71     struct sockaddr_in from;
  72     int fromlen;
  73     struct notify_list *n;
  74     bool_t done;
  75     int rv;
  76
  77     if (nfds && (fds->revents & POLLIN)) {
  78         do {
  79             fromlen=sizeof(from);
  80             BUF_ASSERT_FREE(st->rbuf);
  81             BUF_ALLOC(st->rbuf,"udp_afterpoll");
  82             rv=recvfrom(st->fd, st->rbuf->start, st->rbuf->len, 0,
  83                         (struct sockaddr *)&from, &fromlen);
  84             if (rv>0) {
  85                 st->rbuf->size=rv;
  86                 done=False;
  87                 for (n=st->notify; n; n=n->next) {
  88                     if (n->fn(n->state, st->rbuf, &from)) {
  89                         done=True;
  90                         break;
  91                     }
  92                 }
  93                 if (!done) {
  94                     /* XXX manufacture and send NAK packet */
  95                     Message(M_WARNING,"Need to send NAK\n");
  96                     BUF_FREE(st->rbuf);
  97                 }
  98                 BUF_ASSERT_FREE(st->rbuf);
  99             } else {
 100                 BUF_FREE(st->rbuf);
 101             }
 102         } while (rv>=0);
 103     }
 104 }
 105
 106 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 107 {
 108     struct udp *st=commst;
 109     struct notify_list *n;
 110
 111     n=safe_malloc(sizeof(*n),"request_notify");
 112     n->fn=fn;
 113     n->state=nst;
 114     n->next=st->notify;
 115     st->notify=n;
 116 }
 117
 118 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 119 {
 120     struct udp *st=commst;
 121     struct notify_list *n, **p, *t;
 122
 123     /* XXX untested */
 124     p=&st->notify;
 125     for (n=st->notify; n; )
 126     {
 127         if (n->state==nst && n->fn==fn) {
 128             t=n;
 129             *p=n->next;
 130             n=n->next;
 131             free(t);
 132         } else {
 133             p=&n->next;
 134             n=n->next;
 135         }
 136     }
 137 }
 138
 139 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 140                           struct sockaddr_in *dest)
 141 {
 142     struct udp *st=commst;
 143
 144     /* XXX fix error reporting */
 145     sendto(st->fd, buf->start, buf->size, 0,
 146            (struct sockaddr *)dest, sizeof(*dest));
 147
 148     return True;
 149 }
 150
 151 static void udp_phase_hook(void *sst, uint32_t new_phase)
 152 {
 153     struct udp *st=sst;
 154     struct sockaddr_in addr;
 155
 156     st->fd=socket(AF_INET, SOCK_DGRAM, 0);
 157     if (st->fd<0) {
 158         fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line);
 159     }
 160     if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) {
 161         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 162                      st->loc.file,st->loc.line);
 163     }
 164     if (fcntl(st->fd, F_SETFD, FD_CLOEXEC)==-1) {
 165         fatal_perror("udp (%s:%d): fcntl(set FD_CLOEXEC)",
 166                      st->loc.file,st->loc.line);
 167     }
 168
 169     memset(&addr, 0, sizeof(addr));
 170     addr.sin_family=AF_INET;
 171     addr.sin_port=htons(st->port);
 172     if (st->authbind) {
 173         pid_t c;
 174         int status;
 175
 176         /* XXX this fork() and waitpid() business needs to be hidden
 177            in some system-specific library functions. */
 178         c=fork();
 179         if (c==-1) {
 180             fatal_perror("udp_phase_hook: fork() for authbind");
 181         }
 182         if (c==0) {
 183             char *argv[4];
 184             argv[0]=st->authbind;
 185             argv[1]="00000000";
 186             argv[2]=alloca(8);
 187             if (!argv[2]) exit(ENOMEM);
 188             sprintf(argv[2],"%04X",htons(st->port));
 189             argv[3]=NULL;
 190             dup2(st->fd,0);
 191             execvp(st->authbind,argv);
 192             exit(ENOEXEC);
 193         }
 194         waitpid(c,&status,0);
 195         if (WEXITSTATUS(status)!=0) {
 196             errno=WEXITSTATUS(status);
 197             fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
 198         }
 199     } else {
 200         if (bind(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) {
 201             fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
 202         }
 203     }
 204
 205     register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp");
 206 }
 207
 208 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 209                          list_t *args)
 210 {
 211     struct udp *st;
 212     item_t *i;
 213     dict_t *d;
 214
 215     st=safe_malloc(sizeof(*st),"udp_apply(st)");
 216     st->loc=loc;
 217     st->cl.description="udp";
 218     st->cl.type=CL_COMM;
 219     st->cl.apply=NULL;
 220     st->cl.interface=&st->ops;
 221     st->ops.st=st;
 222     st->ops.request_notify=request_notify;
 223     st->ops.release_notify=release_notify;
 224     st->ops.sendmsg=udp_sendmsg;
 225     st->port=0;
 226
 227     i=list_elem(args,0);
 228     if (!i || i->type!=t_dict) {
 229         cfgfatal(st->loc,"udp","first argument must be a dictionary\n");
 230     }
 231     d=i->data.dict;
 232
 233     st->port=dict_read_number(d,"port",True,"udp",st->loc,0);
 234     st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
 235     st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
 236
 237     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 238
 239     return new_closure(&st->cl);
 240 }
 241
 242 init_module udp_module;
 243 void udp_module(dict_t *dict)
 244 {
 245     add_closure(dict,"udp",udp_apply);
 246 }