Import release 0.1.13

[secnet.git] / udp.c

diff --git a/udp.c b/udp.c
index 65208650f998a7cbc5f670a1d7114ae40adc677b..39888268241895241d1b0c61f16c5264a3131e46 100644 (file)
--- 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. */
 
@@ -22,6 +18,7 @@
 #include <sys/wait.h>
 #include "util.h"
 #include "unaligned.h"
+#include "ipaddr.h"
 
 static beforepoll_fn udp_beforepoll;
 static afterpoll_fn udp_afterpoll;
@@ -29,10 +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;
@@ -48,6 +41,8 @@ struct udp {
     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,
@@ -84,6 +79,21 @@ 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)) {
@@ -93,7 +103,7 @@ static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
                }
                if (!done) {
                    uint32_t source,dest;
-                   /* XXX manufacture and send NAK packet */
+                   /* 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);
@@ -150,10 +160,19 @@ 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;
 }
@@ -221,6 +240,8 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
     struct udp *st;
     item_t *i;
     dict_t *d;
+    list_t *l;
+    uint32_t a;
 
     st=safe_malloc(sizeof(*st),"udp_apply(st)");
     st->loc=loc;
@@ -229,10 +250,13 @@ 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) {
@@ -243,6 +267,24 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
     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->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;
+    }
 
     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);