Re: [PATCH] udp: avoid ufo handling on IP payload compression packets
From: Steffen Klassert <steffen.klassert@secunet.com>
Date: 2017-03-06 06:27:17
On Fri, Mar 03, 2017 at 03:37:32PM +0300, Alexey Kodanev wrote:
commit c146066ab802 ("ipv4: Don't use ufo handling on later transformed
packets") and commit f89c56ce710a ("ipv6: Don't use ufo handling on
later transformed packets") added a check that 'rt->dst.header_len' isn't
zero in order to skip UFO, but it doesn't include IPcomp in transport mode
where it equals zero.IPcomp has an additional header and should better set rt->dst.header_len instead of hacking around that internally.
quoted hunk ↗ jump to hunk
Packets, after payload compression, may not require further fragmentation, and if original length exceeds MTU, later compressed packets will be transmitted incorrectly. This can be reproduced with LTP udp_ipsec.sh test on veth device with enabled UFO, MTU is 1500 and UDP payload is 2000: * IPv4 case, offset is wrong + unnecessary fragmentation udp_ipsec.sh -p comp -m transport -s 2000 & tcpdump -ni ltp_ns_veth2 ... IP (tos 0x0, ttl 64, id 45203, offset 0, flags [+], proto Compressed IP (108), length 49) 10.0.0.2 > 10.0.0.1: IPComp(cpi=0x1000) IP (tos 0x0, ttl 64, id 45203, offset 1480, flags [none], proto UDP (17), length 21) 10.0.0.2 > 10.0.0.1: ip-proto-17 * IPv6 case, sending small fragments udp_ipsec.sh -6 -p comp -m transport -s 2000 & tcpdump -ni ltp_ns_veth2 ... IP6 (flowlabel 0x6b9ba, hlim 64, next-header Compressed IP (108) payload length: 37) fd00::2 > fd00::1: IPComp(cpi=0x1000) IP6 (flowlabel 0x6b9ba, hlim 64, next-header Compressed IP (108) payload length: 21) fd00::2 > fd00::1: IPComp(cpi=0x1000) Fix it by checking 'rt->dst.xfrm' pointer to 'xfrm_state' struct, skip UFO if xfrm is set. So the new check will include both cases: IPcomp and IPsec. Fixes: c146066ab802 ("ipv4: Don't use ufo handling on later transformed packets") Fixes: f89c56ce710a ("ipv6: Don't use ufo handling on later transformed packets") Signed-off-by: Alexey Kodanev <redacted> --- net/ipv4/ip_output.c | 5 ++++- net/ipv6/ip6_output.c | 5 ++++- 2 files changed, 8 insertions(+), 2 deletions(-)diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index b67719f..18383ef 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c@@ -960,7 +960,10 @@ static int __ip_append_data(struct sock *sk, cork->length += length; if ((((length + fragheaderlen) > mtu) || (skb && skb_is_gso(skb))) && (sk->sk_protocol == IPPROTO_UDP) && - (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len && + (rt->dst.dev->features & NETIF_F_UFO) && +#ifdef CONFIG_XFRM + !rt->dst.xfrm && +#endif
Please fix IPcomp to use rt->dst.header_len instead off adding this ifdef to the generic networking code.