Drop packet if there are not enough free buffers to perform fragmentation

core/lib/memb.c

@@ -107,5 +107,18 @@ memb_inmemb(struct memb *m, void *ptr)
     (char *)ptr < (char *)m->mem + (m->num * m->size);
 }
 /*---------------------------------------------------------------------------*/
+int
+memb_numfree(struct memb *m)
+{
+  int i;
+  int num_free = 0;
 
+  for(i = 0; i < m->num; ++i) {
+    if(m->count[i] == 0) {
+      ++num_free;
+    }
+  }
+
+  return num_free;
+}
 /** @} */

core/lib/memb.h

@@ -130,6 +130,7 @@ char  memb_free(struct memb *m, void *ptr);
 
 int memb_inmemb(struct memb *m, void *ptr);
 
+int  memb_numfree(struct memb *m);
 
 /** @} */
 /** @} */

core/net/ipv6/sicslowpan.c

@@ -1454,6 +1454,13 @@ output(const uip_lladdr_t *localdest)
      * IPv6/HC1/HC06/HC_UDP dispatchs/headers.
      * The following fragments contain only the fragn dispatch.
      */
+    int estimated_fragments = ((int)uip_len) / ((int)MAC_MAX_PAYLOAD - SICSLOWPAN_FRAGN_HDR_LEN) + 1;
+    int freebuf = queuebuf_numfree() - 1;
+    PRINTFO("uip_len: %d, fragments: %d, free bufs: %d\n", uip_len, estimated_fragments, freebuf);
+    if(freebuf < estimated_fragments) {
+      PRINTFO("Dropping packet, not enough free bufs\n");
+      return 0;
+    }
 
     PRINTFO("Fragmentation sending packet len %d\n", uip_len);
 

core/net/queuebuf.c

@@ -307,6 +307,16 @@ queuebuf_init(void)
 #endif /* QUEUEBUF_STATS */
 }
 /*---------------------------------------------------------------------------*/
+int
+queuebuf_numfree(void)
+{
+  if(packetbuf_is_reference()) {
+    return memb_numfree(&refbufmem);
+  } else {
+    return memb_numfree(&bufmem);
+  }
+}
+/*---------------------------------------------------------------------------*/
 #if QUEUEBUF_DEBUG
 struct queuebuf *
 queuebuf_new_from_packetbuf_debug(const char *file, int line)

core/net/queuebuf.h

@@ -108,7 +108,9 @@ packetbuf_attr_t queuebuf_attr(struct queuebuf *b, uint8_t type);
 
 void queuebuf_debug_print(void);
 
-#endif /* QUEUEBUF_H_ */
+int queuebuf_numfree(void);
+
+#endif /* __QUEUEBUF_H__ */
 
 /** @} */
 /** @} */