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  * Packets are offered to registered receivers in turn. Once one
   9  * accepts it, it isn't offered to any more. */
  10
  11 #include "secnet.h"
  12 #include <stdio.h>
  13 #include <unistd.h>
  14 #include <fcntl.h>
  15 #include <string.h>
  16 #include <errno.h>
  17 #include <sys/socket.h>
  18 #include <sys/wait.h>
  19 #include "util.h"
  20 #include "unaligned.h"
  21 #include "ipaddr.h"
  22
  23 static beforepoll_fn udp_beforepoll;
  24 static afterpoll_fn udp_afterpoll;
  25 static comm_request_notify_fn request_notify;
  26 static comm_release_notify_fn release_notify;
  27 static comm_sendmsg_fn udp_sendmsg;
  28
  29 struct notify_list {
  30     comm_notify_fn *fn;
  31     void *state;
  32     struct notify_list *next;
  33 };
  34
  35 struct udp {
  36     closure_t cl;
  37     struct comm_if ops;
  38     struct cloc loc;
  39     uint32_t addr;
  40     uint16_t port;
  41     int fd;
  42     string_t authbind;
  43     struct buffer_if *rbuf;
  44     struct notify_list *notify;
  45     bool_t use_proxy;
  46     struct sockaddr_in proxy;
  47 };
  48
  49 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  50                           int *timeout_io, const struct timeval *tv,
  51                           uint64_t *now)
  52 {
  53     struct udp *st=state;
  54     if (*nfds_io<1) {
  55         *nfds_io=1;
  56         return ERANGE;
  57     }
  58     *nfds_io=1;
  59     fds->fd=st->fd;
  60     fds->events=POLLIN;
  61     return 0;
  62 }
  63
  64 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
  65                           const struct timeval *tv, uint64_t *now)
  66 {
  67     struct udp *st=state;
  68     struct sockaddr_in from;
  69     int fromlen;
  70     struct notify_list *n;
  71     bool_t done;
  72     int rv;
  73
  74     if (nfds && (fds->revents & POLLIN)) {
  75         do {
  76             fromlen=sizeof(from);
  77             BUF_ASSERT_FREE(st->rbuf);
  78             BUF_ALLOC(st->rbuf,"udp_afterpoll");
  79             rv=recvfrom(st->fd, st->rbuf->start, st->rbuf->len, 0,
  80                         (struct sockaddr *)&from, &fromlen);
  81             if (rv>0) {
  82                 st->rbuf->size=rv;
  83                 if (st->use_proxy) {
  84                     /* Check that the packet came from our poxy server;
  85                        we shouldn't be contacted directly by anybody else
  86                        (since they can trivially forge source addresses) */
  87                     if (memcmp(&from.sin_addr,&st->proxy.sin_addr,4)!=0 ||
  88                         memcmp(&from.sin_port,&st->proxy.sin_port,2)!=0) {
  89                         Message(M_INFO,"udp: received packet that's not "
  90                                 "from the proxy\n");
  91                         BUF_FREE(st->rbuf);
  92                         continue;
  93                     }
  94                     memcpy(&from.sin_addr,buf_unprepend(st->rbuf,4),4);
  95                     buf_unprepend(st->rbuf,2);
  96                     memcpy(&from.sin_port,buf_unprepend(st->rbuf,2),2);
  97                 }
  98                 done=False;
  99                 for (n=st->notify; n; n=n->next) {
 100                     if (n->fn(n->state, st->rbuf, &from)) {
 101                         done=True;
 102                         break;
 103                     }
 104                 }
 105                 if (!done) {
 106                     uint32_t source,dest;
 107                     /* Manufacture and send NAK packet */
 108                     source=get_uint32(st->rbuf->start); /* Us */
 109                     dest=get_uint32(st->rbuf->start+4); /* Them */
 110                     Message(M_INFO,"udp (port %d): sending NAK\n",st->port);
 111                     buffer_init(st->rbuf,0);
 112                     buf_append_uint32(st->rbuf,dest);
 113                     buf_append_uint32(st->rbuf,source);
 114                     buf_append_uint32(st->rbuf,0); /* NAK is msg type 0 */
 115                     sendto(st->fd, st->rbuf->start, st->rbuf->size, 0,
 116                            (struct sockaddr *)&from, sizeof(from));
 117                     BUF_FREE(st->rbuf);
 118                 }
 119                 BUF_ASSERT_FREE(st->rbuf);
 120             } else {
 121                 BUF_FREE(st->rbuf);
 122             }
 123         } while (rv>=0);
 124     }
 125 }
 126
 127 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 128 {
 129     struct udp *st=commst;
 130     struct notify_list *n;
 131
 132     n=safe_malloc(sizeof(*n),"request_notify");
 133     n->fn=fn;
 134     n->state=nst;
 135     n->next=st->notify;
 136     st->notify=n;
 137 }
 138
 139 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 140 {
 141     struct udp *st=commst;
 142     struct notify_list *n, **p, *t;
 143
 144     /* XXX untested */
 145     p=&st->notify;
 146     for (n=st->notify; n; )
 147     {
 148         if (n->state==nst && n->fn==fn) {
 149             t=n;
 150             *p=n->next;
 151             n=n->next;
 152             free(t);
 153         } else {
 154             p=&n->next;
 155             n=n->next;
 156         }
 157     }
 158 }
 159
 160 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 161                           struct sockaddr_in *dest)
 162 {
 163     struct udp *st=commst;
 164     uint8_t *sa;
 165
 166     if (st->use_proxy) {
 167         sa=buf->start-8;
 168         memcpy(sa,&dest->sin_addr,4);
 169         memset(sa+4,0,4);
 170         memcpy(sa+6,&dest->sin_port,2);
 171         sendto(st->fd,sa,buf->size+8,0,(struct sockaddr *)&st->proxy,
 172                sizeof(st->proxy));
 173     } else {
 174         sendto(st->fd, buf->start, buf->size, 0,
 175                (struct sockaddr *)dest, sizeof(*dest));
 176     }
 177
 178     return True;
 179 }
 180
 181 static void udp_phase_hook(void *sst, uint32_t new_phase)
 182 {
 183     struct udp *st=sst;
 184     struct sockaddr_in addr;
 185
 186     st->fd=socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 187     if (st->fd<0) {
 188         fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line);
 189     }
 190     if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) {
 191         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 192                      st->loc.file,st->loc.line);
 193     }
 194     if (fcntl(st->fd, F_SETFD, FD_CLOEXEC)==-1) {
 195         fatal_perror("udp (%s:%d): fcntl(set FD_CLOEXEC)",
 196                      st->loc.file,st->loc.line);
 197     }
 198
 199     memset(&addr, 0, sizeof(addr));
 200     addr.sin_family=AF_INET;
 201     addr.sin_addr.s_addr=htonl(st->addr);
 202     addr.sin_port=htons(st->port);
 203     if (st->authbind) {
 204         pid_t c;
 205         int status;
 206
 207         /* XXX this fork() and waitpid() business needs to be hidden
 208            in some system-specific library functions. */
 209         c=fork();
 210         if (c==-1) {
 211             fatal_perror("udp_phase_hook: fork() for authbind");
 212         }
 213         if (c==0) {
 214             char *argv[4], addrstr[9], portstr[5];
 215             sprintf(addrstr,"%08lX",(long)st->addr);
 216             sprintf(portstr,"%04X",st->port);
 217             argv[0]=st->authbind;
 218             argv[1]=addrstr;
 219             argv[2]=portstr;
 220             argv[3]=NULL;
 221             dup2(st->fd,0);
 222             execvp(st->authbind,argv);
 223             _exit(255);
 224         }
 225         while (waitpid(c,&status,0)==-1) {
 226             if (errno==EINTR) continue;
 227             fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
 228         }
 229         if (WIFSIGNALED(status)) {
 230             fatal("udp (%s:%d): authbind died on signal %d",st->loc.file,
 231                   st->loc.line, WTERMSIG(status));
 232         }
 233         if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
 234             fatal("udp (%s:%d): authbind died with status %d",st->loc.file,
 235                   st->loc.line, WEXITSTATUS(status));
 236         }
 237     } else {
 238         if (bind(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) {
 239             fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
 240         }
 241     }
 242
 243     register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp");
 244 }
 245
 246 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 247                          list_t *args)
 248 {
 249     struct udp *st;
 250     item_t *i,*j;
 251     dict_t *d;
 252     list_t *l;
 253     uint32_t a;
 254
 255     st=safe_malloc(sizeof(*st),"udp_apply(st)");
 256     st->loc=loc;
 257     st->cl.description="udp";
 258     st->cl.type=CL_COMM;
 259     st->cl.apply=NULL;
 260     st->cl.interface=&st->ops;
 261     st->ops.st=st;
 262     st->ops.min_start_pad=0;
 263     st->ops.min_end_pad=0;
 264     st->ops.request_notify=request_notify;
 265     st->ops.release_notify=release_notify;
 266     st->ops.sendmsg=udp_sendmsg;
 267     st->port=0;
 268     st->use_proxy=False;
 269
 270     i=list_elem(args,0);
 271     if (!i || i->type!=t_dict) {
 272         cfgfatal(st->loc,"udp","first argument must be a dictionary\n");
 273     }
 274     d=i->data.dict;
 275
 276     j=dict_find_item(d,"address",False,"udp",st->loc);
 277     st->addr=j?st->addr=string_item_to_ipaddr(j, "udp"):INADDR_ANY;
 278     st->port=dict_read_number(d,"port",True,"udp",st->loc,0);
 279     st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
 280     st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
 281     l=dict_lookup(d,"proxy");
 282     if (l) {
 283         st->use_proxy=True;
 284         memset(&st->proxy,0,sizeof(st->proxy));
 285         st->proxy.sin_family=AF_INET;
 286         i=list_elem(l,0);
 287         if (!i || i->type!=t_string) {
 288             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 289         }
 290         a=string_item_to_ipaddr(i,"proxy");
 291         st->proxy.sin_addr.s_addr=htonl(a);
 292         i=list_elem(l,1);
 293         if (!i || i->type!=t_number) {
 294             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 295         }
 296         st->proxy.sin_port=htons(i->data.number);
 297         st->ops.min_start_pad=8;
 298     }
 299
 300     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 301
 302     return new_closure(&st->cl);
 303 }
 304
 305 init_module udp_module;
 306 void udp_module(dict_t *dict)
 307 {
 308     add_closure(dict,"udp",udp_apply);
 309 }