From fc04fdb2c8a894283259f5621d31d75610701091 Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <sven@narfation.org>
Date: Fri, 16 Mar 2018 21:14:32 +0100
Subject: [PATCH] batman-adv: Fix skbuff rcsum on packet reroute
Git-commit: fc04fdb2c8a894283259f5621d31d75610701091
Patch-mainline: v4.16-rc7
References: bsc#1051510

batadv_check_unicast_ttvn may redirect a packet to itself or another
originator. This involves rewriting the ttvn and the destination address in
the batadv unicast header. These field were not yet pulled (with skb rcsum
update) and thus any change to them also requires a change in the receive
checksum.

Reported-by: Matthias Schiffer <mschiffer@universe-factory.net>
Fixes: a73105b8d4c7 ("batman-adv: improved client announcement mechanism")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/batman-adv/routing.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -743,6 +743,7 @@ free_skb:
 /**
  * batadv_reroute_unicast_packet - update the unicast header for re-routing
  * @bat_priv: the bat priv with all the soft interface information
+ * @skb: unicast packet to process
  * @unicast_packet: the unicast header to be updated
  * @dst_addr: the payload destination
  * @vid: VLAN identifier
@@ -754,7 +755,7 @@ free_skb:
  * Return: true if the packet header has been updated, false otherwise
  */
 static bool
-batadv_reroute_unicast_packet(struct batadv_priv *bat_priv,
+batadv_reroute_unicast_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,
 			      struct batadv_unicast_packet *unicast_packet,
 			      u8 *dst_addr, unsigned short vid)
 {
@@ -783,8 +784,10 @@ batadv_reroute_unicast_packet(struct bat
 	}
 
 	/* update the packet header */
+	skb_postpull_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
 	ether_addr_copy(unicast_packet->dest, orig_addr);
 	unicast_packet->ttvn = orig_ttvn;
+	skb_postpush_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
 
 	ret = true;
 out:
@@ -825,7 +828,7 @@ static bool batadv_check_unicast_ttvn(st
 	 * the packet to
 	 */
 	if (batadv_tt_local_client_is_roaming(bat_priv, ethhdr->h_dest, vid)) {
-		if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
+		if (batadv_reroute_unicast_packet(bat_priv, skb, unicast_packet,
 						  ethhdr->h_dest, vid))
 			batadv_dbg_ratelimited(BATADV_DBG_TT,
 					       bat_priv,
@@ -871,7 +874,7 @@ static bool batadv_check_unicast_ttvn(st
 	 * destination can possibly be updated and forwarded towards the new
 	 * target host
 	 */
-	if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
+	if (batadv_reroute_unicast_packet(bat_priv, skb, unicast_packet,
 					  ethhdr->h_dest, vid)) {
 		batadv_dbg_ratelimited(BATADV_DBG_TT, bat_priv,
 				       "Rerouting unicast packet to %pM (dst=%pM): TTVN mismatch old_ttvn=%u new_ttvn=%u\n",
@@ -894,12 +897,14 @@ static bool batadv_check_unicast_ttvn(st
 	if (!primary_if)
 		return false;
 
+	/* update the packet header */
+	skb_postpull_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
 	ether_addr_copy(unicast_packet->dest, primary_if->net_dev->dev_addr);
+	unicast_packet->ttvn = curr_ttvn;
+	skb_postpush_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
 
 	batadv_hardif_put(primary_if);
 
-	unicast_packet->ttvn = curr_ttvn;
-
 	return true;
 }