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.
>
> 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 <alexey.koda...@oracle.com>
> ---
> 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.
