From f7627929d5d69e13d4f80c1713b3f83db1ccf862 Mon Sep 17 00:00:00 2001
From: goldsimon <goldsimon>
Date: Mon, 22 Nov 2010 19:55:05 +0000
Subject: [PATCH] Fixed bug #31722: IP packets sent with an AutoIP source addr
 must be sent link-local

---
 CHANGELOG          |  4 ++++
 src/netif/etharp.c | 27 +++++++++++++++++++--------
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 1327c1f9..7f0a945b 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -233,6 +233,10 @@ HISTORY
 
   ++ Bugfixes:
 
+  2010-11-20: Simon Goldschmidt
+  * etharp.c: Fixed bug #31722: IP packets sent with an AutoIP source addr
+    must be sent link-local
+
   2010-11-20: Simon Goldschmidt
   * timers.c: patch #7329: tcp_timer_needed prototype was ifdef'ed out for
     LWIP_TIMERS==0
diff --git a/src/netif/etharp.c b/src/netif/etharp.c
index edd9958f..2857ee69 100644
--- a/src/netif/etharp.c
+++ b/src/netif/etharp.c
@@ -871,14 +871,25 @@ etharp_output(struct netif *netif, struct pbuf *q, ip_addr_t *ipaddr)
     /* outside local network? */
     if (!ip_addr_netcmp(ipaddr, &(netif->ip_addr), &(netif->netmask)) &&
         !ip_addr_islinklocal(ipaddr)) {
-      /* interface has default gateway? */
-      if (!ip_addr_isany(&netif->gw)) {
-        /* send to hardware address of default gateway IP address */
-        ipaddr = &(netif->gw);
-      /* no default gateway available */
-      } else {
-        /* no route to destination error (default gateway missing) */
-        return ERR_RTE;
+#if LWIP_AUTOIP
+      struct ip_hdr *iphdr = (struct ip_hdr*)((u8_t*)q->payload +
+        sizeof(struct eth_hdr));
+      /* According to RFC 3297, chapter 2.6.2 (Forwarding Rules), a packet with
+         a link-local source address must always be "directly to its destination
+         on the same physical link. The host MUST NOT send the packet to any
+         router for forwarding". */
+      if (!ip_addr_islinklocal(&iphdr->src))
+#endif /* LWIP_AUTOIP */
+      {
+        /* interface has default gateway? */
+        if (!ip_addr_isany(&netif->gw)) {
+          /* send to hardware address of default gateway IP address */
+          ipaddr = &(netif->gw);
+        /* no default gateway available */
+        } else {
+          /* no route to destination error (default gateway missing) */
+          return ERR_RTE;
+        }
       }
     }
 #if LWIP_NETIF_HWADDRHINT