IOB: Fix bugs in trimming logic

net/iob/iob_test.c

@@ -74,21 +74,32 @@ uint8_t buffer2[16384];
 
 static void dump_chain(struct iob_s *iob)
 {
+  struct iob_s *head = iob;
+  unsigned int pktlen;
   int n;
  
   printf("=========================================================\n");
   printf("pktlen: %d flags: %02x\n", iob->io_pktlen, iob->io_flags);
 
   n = 0;
+  pktlen = 0;
+
   while (iob)
     {
       printf("%d. len=%d, offset=%d, priv=%p\n",
              n, iob->io_len, iob->io_offset, iob->io_priv);
 
+      pktlen += iob->io_len;
       iob = (struct iob_s *)iob->io_link.flink;
       n++;
     }
 
+  if (pktlen != head->io_pktlen)
+    {
+      printf("ERROR: Bad packet length=%u, actual=%u\n",
+             head->io_pktlen, pktlen);
+    }
+
   printf("=========================================================\n");
 }
 
@@ -164,7 +175,7 @@ int main(int argc, char **argv)
     }
 
   iob = iob_pack(iob);
-  printf("Packed\n", nbytes);
+  printf("Packed\n");
   dump_chain(iob);
 
   nbytes = iob_copyout(buffer2, iob, 4096, 0);

net/iob/iob_trimhead.c

@@ -120,8 +120,9 @@ FAR struct iob_s *iob_trimhead(FAR struct iob_s *iob, unsigned int trimlen)
 
               /* Free this entry and set the next I/O buffer as the head */
 
-              iob_free(entry);
+              (void)iob_free(entry);
               entry = next;
+              iob   = next;
             }
           else
             {

net/iob/iob_trimtail.c

@@ -76,7 +76,6 @@
 
 FAR struct iob_s *iob_trimtail(FAR struct iob_s *iob, unsigned int trimlen)
 {
-  FAR struct iob_s *head = iob;
   FAR struct iob_s *entry;
   FAR struct iob_s *penultimate;
   FAR struct iob_s *last;
@@ -121,9 +120,9 @@ FAR struct iob_s *iob_trimtail(FAR struct iob_s *iob, unsigned int trimlen)
             {
               /* Yes.. Consume the entire buffer */
 
-              head->io_pktlen -= last->io_len;
-              len             -= last->io_len;
-              last->io_len     = 0;
+              iob->io_pktlen -= last->io_len;
+              len            -= last->io_len;
+              last->io_len    = 0;
 
               /* Free the last, empty buffer in the list */
 
@@ -149,9 +148,9 @@ FAR struct iob_s *iob_trimtail(FAR struct iob_s *iob, unsigned int trimlen)
                * stop the trim.
                */
 
-              head->io_pktlen -= last->io_len;
-              last->io_len    -= len;
-              len              = 0;
+              iob->io_pktlen -= len;
+              last->io_len   -= len;
+              len             = 0;
             }
         }
     }