[PATCH 3.2 067/126] ipv6: Don't use ufo handling on later transformed packets

Ben Hutchings
2017-02-15T23:06:05Z

From: Jakub Sitnicki <jkbs@redhat.com>

commit f89c56ce710afa65e1b2ead555b52c4807f34ff7 upstream.

Similar to commit c146066ab802 ("ipv4: Don't use ufo handling on later
transformed packets"), don't perform UFO on packets that will be IPsec
transformed. To detect it we rely on the fact that headerlen in
dst_entry is non-zero only for transformation bundles (xfrm_dst
objects).

Unwanted segmentation can be observed with a NETIF_F_UFO capable device,
such as a dummy device:

DEV=dum0 LEN=1493

ip li add $DEV type dummy
ip addr add fc00::1/64 dev $DEV nodad
ip link set $DEV up
ip xfrm policy add dir out src fc00::1 dst fc00::2 \
tmpl src fc00::1 dst fc00::2 proto esp spi 1
ip xfrm state add src fc00::1 dst fc00::2 \
proto esp spi 1 enc 'aes' 0x0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b

tcpdump -n -nn -i $DEV -t &
socat /dev/zero,readbytes=$LEN udp6:[fc00::2]:$LEN

tcpdump output before:

IP6 fc00::1 > fc00::2: frag (0|1448) ESP(spi=0x00000001,seq=0x1), length 1448
IP6 fc00::1 > fc00::2: frag (1448|48)
IP6 fc00::1 > fc00::2: ESP(spi=0x00000001,seq=0x2), length 88

... and after:

IP6 fc00::1 > fc00::2: frag (0|1448) ESP(spi=0x00000001,seq=0x1), length 1448
IP6 fc00::1 > fc00::2: frag (1448|80)

Fixes: e89e9cf539a2 ("[IPv4/IPv6]: UFO Scatter-gather approach")

Signed-off-by: Jakub Sitnicki <jkbs@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv6/ip6_output.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1338,7 +1338,7 @@ int ip6_append_data(struct sock *sk, int
if (((length > mtu) ||
(skb && skb_has_frags(skb))) &&
(sk->sk_protocol == IPPROTO_UDP) &&
- (rt->dst.dev->features & NETIF_F_UFO) &&
+ (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
(sk->sk_type == SOCK_DGRAM)) {
err = ip6_ufo_append_data(sk, getfrag, from, length,
hh_len, fragheaderlen, exthdrlen,