Added the option PBUF_LINK_ENCAPSULATION_HLEN to allocate additional header space for TX on netifs requiring additional headers

CHANGELOG

@@ -6,6 +6,10 @@ HISTORY
 
   ++ New features:
 
+  2015-02-13: Simon Goldschmidt
+  * opt.h, pbuf.h/.c, etharp.c: Added the option PBUF_LINK_ENCAPSULATION_HLEN to
+    allocate additional header space for TX on netifs requiring additional headers
+
   2015-02-12: chrysn
   * timers.h/.c: introduce sys_timeouts_sleeptime (returns the time left before
     the next timeout is due, for NO_SYS==1)

src/core/pbuf.c

@@ -214,17 +214,22 @@ pbuf_alloc(pbuf_layer layer, u16_t length, pbuf_type type)
   switch (layer) {
   case PBUF_TRANSPORT:
     /* add room for transport (often TCP) layer header */
-    offset = PBUF_LINK_HLEN + PBUF_IP_HLEN + PBUF_TRANSPORT_HLEN;
+    offset = PBUF_LINK_ENCAPSULATION_HLEN + PBUF_LINK_HLEN + PBUF_IP_HLEN + PBUF_TRANSPORT_HLEN;
     break;
   case PBUF_IP:
     /* add room for IP layer header */
-    offset = PBUF_LINK_HLEN + PBUF_IP_HLEN;
+    offset = PBUF_LINK_ENCAPSULATION_HLEN + PBUF_LINK_HLEN + PBUF_IP_HLEN;
     break;
   case PBUF_LINK:
     /* add room for link layer header */
-    offset = PBUF_LINK_HLEN;
+    offset = PBUF_LINK_ENCAPSULATION_HLEN + PBUF_LINK_HLEN;
+    break;
+  case PBUF_RAW_TX:
+    /* add room for encapsulating link layer headers (e.g. 802.11) */
+    offset = PBUF_LINK_ENCAPSULATION_HLEN;
     break;
   case PBUF_RAW:
+    /* no offset (e.g. RX buffers or chain successors) */
     offset = 0;
     break;
   default:

src/include/lwip/opt.h

@@ -1189,6 +1189,14 @@
 #endif /* LWIP_HOOK_VLAN_SET */
 #endif
 
+/**
+ * PBUF_LINK_ENCAPSULATION_HLEN: the number of bytes that should be allocated
+ * for an additional encapsulation header before ethernet headers (e.g. 802.11)
+ */
+#ifndef PBUF_LINK_ENCAPSULATION_HLEN
+#define PBUF_LINK_ENCAPSULATION_HLEN    0
+#endif
+
 /**
  * PBUF_POOL_BUFSIZE: the size of each pbuf in the pbuf pool. The default is
  * designed to accommodate single full size TCP frame in one pbuf, including

src/include/lwip/pbuf.h

@@ -60,6 +60,7 @@ typedef enum {
   PBUF_TRANSPORT,
   PBUF_IP,
   PBUF_LINK,
+  PBUF_RAW_TX,
   PBUF_RAW
 } pbuf_layer;
 

src/netif/etharp.c

@@ -1128,7 +1128,7 @@ etharp_query(struct netif *netif, ip_addr_t *ipaddr, struct pbuf *q)
     }
     if(copy_needed) {
       /* copy the whole packet into new pbufs */
-      p = pbuf_alloc(PBUF_RAW, p->tot_len, PBUF_RAM);
+      p = pbuf_alloc(PBUF_RAW_TX, p->tot_len, PBUF_RAM);
       if(p != NULL) {
         if (pbuf_copy(p, q) != ERR_OK) {
           pbuf_free(p);
@@ -1240,7 +1240,7 @@ etharp_raw(struct netif *netif, const struct eth_addr *ethsrc_addr,
   LWIP_ASSERT("netif != NULL", netif != NULL);
 
   /* allocate a pbuf for the outgoing ARP request packet */
-  p = pbuf_alloc(PBUF_RAW, SIZEOF_ETHARP_PACKET_TX, PBUF_RAM);
+  p = pbuf_alloc(PBUF_RAW_TX, SIZEOF_ETHARP_PACKET_TX, PBUF_RAM);
   /* could allocate a pbuf for an ARP request? */
   if (p == NULL) {
     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,