tftp: fix wrong check for port numbers

2 files changed, 23 insertions, 20 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 8ad92263e..8f3d7f038 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -290,7 +290,7 @@ extern int setsockopt_broadcast(int fd);
 
 /* "new" (ipv4+ipv6) API */
 typedef struct len_and_sockaddr {
-        int len;
+        socklen_t len;
         union {
                 struct sockaddr sa;
                 struct sockaddr_in sin;
diff --git a/networking/tftp.c b/networking/tftp.c
index eb192d8fc..bafcddbee 100644
--- a/networking/tftp.c
+++ b/networking/tftp.c
@@ -132,7 +132,7 @@ static int tftp(
 #if ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT
                 const int cmd,
 #endif
-                const len_and_sockaddr *peer_lsa,
+                len_and_sockaddr *peer_lsa,
                 const char *remotefile, const int localfd,
                 unsigned port, int tftp_bufsize)
 {
@@ -149,6 +149,9 @@ static int tftp(
 
         USE_FEATURE_TFTP_BLOCKSIZE(int want_option_ack = 0;)
 
+        unsigned org_port;
+        len_and_sockaddr *const from = alloca(offsetof(len_and_sockaddr, sa) + peer_lsa->len);
+
         /* Can't use RESERVE_CONFIG_BUFFER here since the allocation
          * size varies meaning BUFFERS_GO_ON_STACK would fail */
         /* We must keep the transmit and receive buffers seperate */
@@ -156,7 +159,7 @@ static int tftp(
         char *xbuf = xmalloc(tftp_bufsize += 4);
         char *rbuf = xmalloc(tftp_bufsize);
 
-        port = htons(port);
+        port = org_port = htons(port);
 
         socketfd = xsocket(peer_lsa->sa.sa_family, SOCK_DGRAM, 0);
 
@@ -167,10 +170,10 @@ static int tftp(
         }
 
         while (1) {
-
                 cp = xbuf;
 
                 /* first create the opcode part */
+                /* (this 16bit store is aligned) */
                 *((uint16_t*)cp) = htons(opcode);
                 cp += 2;
 
@@ -222,6 +225,7 @@ static int tftp(
                 /* add ack and data */
 
                 if (CMD_GET(cmd) ? (opcode == TFTP_ACK) : (opcode == TFTP_DATA)) {
+                        /* TODO: unaligned access! */
                         *((uint16_t*)cp) = htons(block_nr);
                         cp += 2;
                         block_nr++;
@@ -273,28 +277,26 @@ static int tftp(
                         FD_SET(socketfd, &rfds);
 
                         switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) {
-                                struct sockaddr *from;
-                                socklen_t fromlen;
-
+                                unsigned from_port;
                         case 1:
-                                fromlen = peer_lsa->len;
-                                from = alloca(fromlen);
-                                memset(from, 0, fromlen);
-
+                                from->len = peer_lsa->len;
+                                memset(&from->sa, 0, peer_lsa->len);
                                 len = recvfrom(socketfd, rbuf, tftp_bufsize, 0,
-                                                        from, &fromlen);
+                                                        &from->sa, &from->len);
                                 if (len < 0) {
                                         bb_perror_msg("recvfrom");
                                         break;
                                 }
-#if ENABLE_FEATURE_IPV6
-                                if (from->sa_family == AF_INET6)
-                                        if (((struct sockaddr_in6*)from)->sin6_port != port)
-                                                goto recv_again;
-#endif
-                                if (from->sa_family == AF_INET)
-                                        if (((struct sockaddr_in*)from)->sin_port != port)
-                                                goto recv_again;
+                                from_port = get_nport(from);
+                                if (port == org_port) {
+                                        /* Our first query went to port 69
+                                         * but reply will come from different one.
+                                         * Remember and use this new port */
+                                        port = from_port;
+                                        set_nport(peer_lsa, from_port);
+                                }
+                                if (port != from_port)
+                                        goto recv_again;
                                 timeout = 0;
                                 break;
                         case 0:
@@ -317,6 +319,7 @@ static int tftp(
                 }
 
                 /* process received packet */
+                /* (both accesses seems to be aligned) */
 
                 opcode = ntohs( ((uint16_t*)rbuf)[0] );
                 tmp = ntohs( ((uint16_t*)rbuf)[1] );