Don't chain empty pbufs when sending them (fixes bug #30625)

CHANGELOG

@@ -229,6 +229,9 @@ HISTORY
 
   ++ Bugfixes:
 
+  2010-08-03: Simon Goldschmidt
+  * udp.c, raw.c: Don't chain empty pbufs when sending them (fixes bug #30625)
+
   2010-08-01: Simon Goldschmidt (patch by Greg Renda)
   * ppp.c: Applied patch #7264 (PPP protocols are rejected incorrectly on big
     endian architectures)

src/core/raw.c

@@ -218,8 +218,10 @@ raw_sendto(struct raw_pcb *pcb, struct pbuf *p, ip_addr_t *ipaddr)
       LWIP_DEBUGF(RAW_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS, ("raw_sendto: could not allocate header\n"));
       return ERR_MEM;
     }
-    /* chain header q in front of given pbuf p */
-    pbuf_chain(q, p);
+    if (p->tot_len != 0) {
+      /* chain header q in front of given pbuf p */
+      pbuf_chain(q, p);
+    }
     /* { first pbuf q points to header pbuf } */
     LWIP_DEBUGF(RAW_DEBUG, ("raw_sendto: added header pbuf %p before given pbuf %p\n", (void *)q, (void *)p));
   }  else {

src/core/udp.c

@@ -520,8 +520,10 @@ udp_sendto_if_chksum(struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *dst_ip,
       LWIP_DEBUGF(UDP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS, ("udp_send: could not allocate header\n"));
       return ERR_MEM;
     }
-    /* chain header q in front of given pbuf p */
-    pbuf_chain(q, p);
+    if (p->tot_len != 0) {
+      /* chain header q in front of given pbuf p (only if p contains data) */
+      pbuf_chain(q, p);
+    }
     /* first pbuf q points to header pbuf */
     LWIP_DEBUGF(UDP_DEBUG,
                 ("udp_send: added header pbuf %p before given pbuf %p\n", (void *)q, (void *)p));