X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=blobdiff_plain;f=udp.c;h=7ff4d5fd18f84e5ade3487701484124c55767c9e;hp=f05596202d8e0f5d7a59d6205b60cb7b8b4ac89a;hb=29672515f5b2864a1e5b849a209cefd2adfac757;hpb=8689b3a94c043f04e334a7b181a7250ad5940616

diff --git a/udp.c b/udp.c
index f055962..7ff4d5f 100644
--- a/udp.c
+++ b/udp.c
@@ -5,10 +5,6 @@
  * optionally bind to a particular local IP address (not implemented
  * yet).
  *
- * Sites register an interest in local port numbers for receiving
- * packets, and can also send packets. We don't care about the source
- * port number for sending packets. 
- *
  * Packets are offered to registered receivers in turn. Once one
  * accepts it, it isn't offered to any more. */
 
@@ -19,7 +15,10 @@
 #include <string.h>
 #include <errno.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 #include "util.h"
+#include "unaligned.h"
+#include "ipaddr.h"
 
 static beforepoll_fn udp_beforepoll;
 static afterpoll_fn udp_afterpoll;
@@ -27,10 +26,6 @@ static comm_request_notify_fn request_notify;
 static comm_release_notify_fn release_notify;
 static comm_sendmsg_fn udp_sendmsg;
 
-/* The UDP module exports a pure closure which can be used to construct a
- * UDP send/receive module. Arguments:
- */
-
 struct notify_list {
     comm_notify_fn *fn;
     void *state;
@@ -41,14 +36,18 @@ struct udp {
     closure_t cl;
     struct comm_if ops;
     struct cloc loc;
+    uint32_t addr;
+    uint16_t port;
     int fd;
+    string_t authbind;
     struct buffer_if *rbuf;
     struct notify_list *notify;
+    bool_t use_proxy;
+    struct sockaddr_in proxy;
 };
 
 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
-			  int *timeout_io, const struct timeval *tv,
-			  uint64_t *now)
+			  int *timeout_io)
 {
     struct udp *st=state;
     if (*nfds_io<1) {
@@ -61,12 +60,11 @@ static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
     return 0;
 }
 
-static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
-			  const struct timeval *tv, uint64_t *now)
+static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 {
     struct udp *st=state;
     struct sockaddr_in from;
-    int fromlen;
+    socklen_t fromlen;
     struct notify_list *n;
     bool_t done;
     int rv;
@@ -80,6 +78,21 @@ static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
 			(struct sockaddr *)&from, &fromlen);
 	    if (rv>0) {
 		st->rbuf->size=rv;
+		if (st->use_proxy) {
+		    /* Check that the packet came from our poxy server;
+		       we shouldn't be contacted directly by anybody else
+		       (since they can trivially forge source addresses) */
+		    if (memcmp(&from.sin_addr,&st->proxy.sin_addr,4)!=0 ||
+			memcmp(&from.sin_port,&st->proxy.sin_port,2)!=0) {
+			Message(M_INFO,"udp: received packet that's not "
+				"from the proxy\n");
+			BUF_FREE(st->rbuf);
+			continue;
+		    }
+		    memcpy(&from.sin_addr,buf_unprepend(st->rbuf,4),4);
+		    buf_unprepend(st->rbuf,2);
+		    memcpy(&from.sin_port,buf_unprepend(st->rbuf,2),2);
+		}
 		done=False;
 		for (n=st->notify; n; n=n->next) {
 		    if (n->fn(n->state, st->rbuf, &from)) {
@@ -88,8 +101,17 @@ static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
 		    }
 		}
 		if (!done) {
-		    /* XXX manufacture and send NAK packet */
-		    Message(M_WARNING,"Need to send NAK\n");
+		    uint32_t source,dest;
+		    /* Manufacture and send NAK packet */
+		    source=get_uint32(st->rbuf->start); /* Us */
+		    dest=get_uint32(st->rbuf->start+4); /* Them */
+		    Message(M_INFO,"udp (port %d): sending NAK\n",st->port);
+		    buffer_init(st->rbuf,0);
+		    buf_append_uint32(st->rbuf,dest);
+		    buf_append_uint32(st->rbuf,source);
+		    buf_append_uint32(st->rbuf,0); /* NAK is msg type 0 */
+		    sendto(st->fd, st->rbuf->start, st->rbuf->size, 0,
+			   (struct sockaddr *)&from, sizeof(from));
 		    BUF_FREE(st->rbuf);
 		}
 		BUF_ASSERT_FREE(st->rbuf);
@@ -137,22 +159,96 @@ static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 			  struct sockaddr_in *dest)
 {
     struct udp *st=commst;
+    uint8_t *sa;
 
-    /* XXX fix error reporting */
-    sendto(st->fd, buf->start, buf->size, 0,
-	   (struct sockaddr *)dest, sizeof(*dest));
+    if (st->use_proxy) {
+	sa=buf->start-8;
+	memcpy(sa,&dest->sin_addr,4);
+	memset(sa+4,0,4);
+	memcpy(sa+6,&dest->sin_port,2);
+	sendto(st->fd,sa,buf->size+8,0,(struct sockaddr *)&st->proxy,
+	       sizeof(st->proxy));
+    } else {
+	sendto(st->fd, buf->start, buf->size, 0,
+	       (struct sockaddr *)dest, sizeof(*dest));
+    }
 
     return True;
 }
 
+static void udp_phase_hook(void *sst, uint32_t new_phase)
+{
+    struct udp *st=sst;
+    struct sockaddr_in addr;
+
+    st->fd=socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
+    if (st->fd<0) {
+	fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line);
+    }
+    if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) {
+	fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
+		     st->loc.file,st->loc.line);
+    }
+    if (fcntl(st->fd, F_SETFD, FD_CLOEXEC)==-1) {
+	fatal_perror("udp (%s:%d): fcntl(set FD_CLOEXEC)",
+		     st->loc.file,st->loc.line);
+    }
+
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family=AF_INET;
+    addr.sin_addr.s_addr=htonl(st->addr);
+    addr.sin_port=htons(st->port);
+    if (st->authbind) {
+	pid_t c;
+	int status;
+
+	/* XXX this fork() and waitpid() business needs to be hidden
+	   in some system-specific library functions. */
+	c=fork();
+	if (c==-1) {
+	    fatal_perror("udp_phase_hook: fork() for authbind");
+	}
+	if (c==0) {
+	    char *argv[4], addrstr[9], portstr[5];
+	    sprintf(addrstr,"%08lX",(long)st->addr);
+	    sprintf(portstr,"%04X",st->port);
+	    argv[0]=st->authbind;
+	    argv[1]=addrstr;
+	    argv[2]=portstr;
+	    argv[3]=NULL;
+	    dup2(st->fd,0);
+	    execvp(st->authbind,argv);
+	    _exit(255);
+	}
+	while (waitpid(c,&status,0)==-1) {
+	    if (errno==EINTR) continue;
+	    fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
+	}
+	if (WIFSIGNALED(status)) {
+	    fatal("udp (%s:%d): authbind died on signal %d",st->loc.file,
+		  st->loc.line, WTERMSIG(status));
+	}
+	if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
+	    fatal("udp (%s:%d): authbind died with status %d",st->loc.file,
+		  st->loc.line, WEXITSTATUS(status));
+	}
+    } else {
+	if (bind(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) {
+	    fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
+	}
+    }
+
+    register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp");
+}
+
 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 			 list_t *args)
 {
     struct udp *st;
-    item_t *i;
+    item_t *i,*j;
     dict_t *d;
-    uint16_t local_port=0;
-    struct sockaddr_in addr;
+    list_t *l;
+    uint32_t a;
 
     st=safe_malloc(sizeof(*st),"udp_apply(st)");
     st->loc=loc;
@@ -161,9 +257,13 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
     st->cl.apply=NULL;
     st->cl.interface=&st->ops;
     st->ops.st=st;
+    st->ops.min_start_pad=0;
+    st->ops.min_end_pad=0;
     st->ops.request_notify=request_notify;
     st->ops.release_notify=release_notify;
     st->ops.sendmsg=udp_sendmsg;
+    st->port=0;
+    st->use_proxy=False;
 
     i=list_elem(args,0);
     if (!i || i->type!=t_dict) {
@@ -171,37 +271,35 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
     }
     d=i->data.dict;
 
-    local_port=dict_read_number(d,"port",False,"udp",st->loc,0);
+    j=dict_find_item(d,"address",False,"udp",st->loc);
+    st->addr=j?string_item_to_ipaddr(j, "udp"):INADDR_ANY;
+    st->port=dict_read_number(d,"port",True,"udp",st->loc,0);
     st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
-
-    st->fd=socket(AF_INET, SOCK_DGRAM, 0);
-    if (st->fd<0) {
-	fatal_perror("udp_apply (%s:%d): socket",loc.file,loc.line);
-    }
-    if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) {
-	fatal_perror("udp_apply (%s:%d): fcntl(set O_NONBLOCK)",
-		     loc.file,loc.line);
-    }
-    if (fcntl(st->fd, F_SETFD, FD_CLOEXEC)==-1) {
-	fatal_perror("udp_apply (%s:%d): fcntl(set FD_CLOEXEC)",
-		     loc.file,loc.line);
-    }
-
-    memset(&addr, 0, sizeof(addr));
-    addr.sin_family=AF_INET;
-    if (local_port) {
-	addr.sin_port=htons(local_port);
-    }
-    if (bind(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) {
-	fatal_perror("udp_apply (%s:%d): bind",loc.file,loc.line);
+    st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
+    l=dict_lookup(d,"proxy");
+    if (l) {
+	st->use_proxy=True;
+	memset(&st->proxy,0,sizeof(st->proxy));
+	st->proxy.sin_family=AF_INET;
+	i=list_elem(l,0);
+	if (!i || i->type!=t_string) {
+	    cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
+	}
+	a=string_item_to_ipaddr(i,"proxy");
+	st->proxy.sin_addr.s_addr=htonl(a);
+	i=list_elem(l,1);
+	if (!i || i->type!=t_number) {
+	    cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
+	}
+	st->proxy.sin_port=htons(i->data.number);
+	st->ops.min_start_pad=8;
     }
 
-    register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp");
+    add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 
     return new_closure(&st->cl);
 }
 
-init_module udp_module;
 void udp_module(dict_t *dict)
 {
     add_closure(dict,"udp",udp_apply);