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