net: ipv4: ip_forward: fix inverted local_df test

local_df means 'ignore DF bit if set', so if its set we're
allowed to perform ip fragmentation.

This wasn't noticed earlier because the output path also drops such skbs
(and emits needed icmp error) and because netfilter ip defrag did not
set local_df until couple of days ago.

Only difference is that DF-packets-larger-than MTU now discarded
earlier (f.e. we avoid pointless netfilter postrouting trip).

While at it, drop the repeated test ip_exceeds_mtu, checking it once
is enough...

Fixes: fe6cc55f3a9 ("net: ip, ipv6: handle gso skbs in forwarding path")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index be8abe73bb9f464a2e68679255acde3b708ce84b..c29ae8371e44b7215a271c4e95de2282ac787b27 100644 (file)
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -42,12 +42,12 @@
 static bool ip_may_fragment(const struct sk_buff *skb)
 {
        return unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0) ||
-              !skb->local_df;
+               skb->local_df;
 }
 
 static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
 {
-       if (skb->len <= mtu || skb->local_df)
+       if (skb->len <= mtu)
                return false;
 
        if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)