Add pbuf_cat and use it where pbuf_chain followed by pbuf_free was used before

src/core/pbuf.c

@@ -617,7 +617,6 @@ pbuf_clen(struct pbuf *p)
 }
 
 /**
- *
  * Increment the reference count of the pbuf.
  *
  * @param p pbuf to increase reference counter of
@@ -636,20 +635,16 @@ pbuf_ref(struct pbuf *p)
 }
 
 /**
+ * Concatenate two pbufs (each may be a pbuf chain) and take over
+ * the reference of the tail pbuf.
  * 
- * Chain two pbufs (or pbuf chains) together. They must belong to the same packet.
- *
- * @param h head pbuf (chain)
- * @param t tail pbuf (chain)
- * @note May not be called on a packet queue.
- *
- * The ->tot_len fields of all pbufs of the head chain are adjusted.
- * The ->next field of the last pbuf of the head chain is adjusted.
- * The ->ref field of the first pbuf of the tail chain is adjusted.
+ *  @note The caller MAY NOT reference the tail pbuf afterwards.
  * 
+ *  @see pbuf_chain()
  */
+
 void
-pbuf_chain(struct pbuf *h, struct pbuf *t)
+pbuf_cat(struct pbuf *h, struct pbuf *t)
 {
   struct pbuf *p;
 
@@ -670,9 +665,29 @@ pbuf_chain(struct pbuf *h, struct pbuf *t)
   p->tot_len += t->tot_len;
   /* chain last pbuf of head (p) with first of tail (t) */
   p->next = t;
+}
+
+/**
+ * Chain two pbufs (or pbuf chains) together. They must belong to the same packet.
+ * It's the same as pbuf_cat with the addition that it increases the reference count
+ * of the tail.
+ * 
+ * @param h head pbuf (chain)
+ * @param t tail pbuf (chain)
+ * @note May not be called on a packet queue.
+ *
+ * The ->tot_len fields of all pbufs of the head chain are adjusted.
+ * The ->next field of the last pbuf of the head chain is adjusted.
+ * The ->ref field of the first pbuf of the tail chain is adjusted.
+ *
+ */
+void
+pbuf_chain(struct pbuf *h, struct pbuf *t)
+{
+  pbuf_cat(h, t);
   /* t is now referenced to one more time */
   pbuf_ref(t);
-  LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)p, (void *)t));
+  LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
 }
 
 /* For packet queueing. Note that queued packets must be dequeued first

src/core/tcp_in.c

@@ -1013,8 +1013,7 @@ tcp_receive(struct tcp_pcb *pcb)
       /* Chain this pbuf onto the pbuf that we will pass to
          the application. */
       if (recv_data) {
-              pbuf_chain(recv_data, cseg->p);
-              pbuf_free(cseg->p);
+              pbuf_cat(recv_data, cseg->p);
             } else {
         recv_data = cseg->p;
       }

src/core/tcp_out.c

@@ -210,9 +210,8 @@ tcp_enqueue(struct tcp_pcb *pcb, void *arg, u16_t len,
       }
       ++queuelen;
 
-      /* Chain the headers and data pbufs together. */
-      pbuf_chain(seg->p, p);
-      pbuf_free(p);
+      /* Concatenate the headers and data pbufs together. */
+      pbuf_cat(seg->p, p);
       p = NULL;
     }
 
@@ -286,11 +285,7 @@ tcp_enqueue(struct tcp_pcb *pcb, void *arg, u16_t len,
     useg->len + queue->len <= pcb->mss) {
     /* Remove TCP header from first segment. */
     pbuf_header(queue->p, -TCP_HLEN);
-    pbuf_chain(useg->p, queue->p);
-    /* Free buffer which was merged. Note that the previous pbuf_chain call
-     * will have incremented the ref count, so here the ref count will still
-     * be 1 for the 1 pointer still being used on this buffer. */
-    pbuf_free(queue->p);
+    pbuf_cat(useg->p, queue->p);
     useg->len += queue->len;
     useg->next = queue->next;
 

src/include/lwip/pbuf.h

@@ -108,6 +108,7 @@ void pbuf_ref(struct pbuf *p);
 void pbuf_ref_chain(struct pbuf *p);
 u8_t pbuf_free(struct pbuf *p);
 u8_t pbuf_clen(struct pbuf *p);  
+void pbuf_cat(struct pbuf *h, struct pbuf *t);
 void pbuf_chain(struct pbuf *h, struct pbuf *t);
 struct pbuf *pbuf_take(struct pbuf *f);
 struct pbuf *pbuf_dechain(struct pbuf *p);

src/netif/ppp/ppp.c

@@ -1480,14 +1480,12 @@ static void pppInProc(int pd, u_char *s, int l)
 
 			pc->inTail->tot_len = pc->inTail->len;
 			if (pc->inTail != pc->inHead) {
-			    pbuf_chain(pc->inHead, pc->inTail);
-			    pbuf_free(pc->inTail);
+			    pbuf_cat(pc->inHead, pc->inTail);
 			}
 		    } else {
 			pc->inTail->tot_len = pc->inTail->len;
 			if (pc->inTail != pc->inHead) {
-			    pbuf_chain(pc->inHead, pc->inTail);
-			    pbuf_free(pc->inTail);
+			    pbuf_cat(pc->inHead, pc->inTail);
 			}
 
 			pbuf_realloc(pc->inHead, pc->inHead->tot_len - 2);
@@ -1583,8 +1581,7 @@ static void pppInProc(int pd, u_char *s, int l)
 		    if(pc->inTail) {
 			pc->inTail->tot_len = pc->inTail->len;
 			if (pc->inTail != pc->inHead) {
-			    pbuf_chain(pc->inHead, pc->inTail);
-			    pbuf_free(pc->inTail);
+			    pbuf_cat(pc->inHead, pc->inTail);
 			}
 		    }
                     /* If we haven't started a packet, we need a packet header. */

src/netif/ppp/vj.c

@@ -611,8 +611,7 @@ int vj_uncompress_tcp(
 			*nb = NULL;
 			goto bad;
 		}
-		pbuf_chain(np, n0);
-		pbuf_free(n0);
+		pbuf_cat(np, n0);
 		n0 = np;
 	}
 	LWIP_ASSERT("n0->len >= cs->cs_hlen", n0->len >= cs->cs_hlen);

src/netif/slipif.c

@@ -145,8 +145,7 @@ slipif_input( struct netif * netif )
   }
   
   if (q != NULL) {
-    pbuf_chain(q, p);
-    pbuf_free(p);
+    pbuf_cat(q, p);
   } else {
     q = p;
   }