| From 13d3b88b0b4694924fbf4d64fabd248a64f3db00 Mon Sep 17 00:00:00 2001 |
| From: Nicolas Dichtel <nicolas.dichtel@6wind.com> |
| Date: Thu, 17 Jan 2019 11:27:22 +0100 |
| Subject: af_packet: fix raw sockets over 6in4 tunnel |
| |
| [ Upstream commit 88a8121dc1d3d0dbddd411b79ed236b6b6ea415c ] |
| |
| Since commit cb9f1b783850, scapy (which uses an AF_PACKET socket in |
| SOCK_RAW mode) is unable to send a basic icmp packet over a sit tunnel: |
| |
| Here is a example of the setup: |
| $ ip link set ntfp2 up |
| $ ip addr add 10.125.0.1/24 dev ntfp2 |
| $ ip tunnel add tun1 mode sit ttl 64 local 10.125.0.1 remote 10.125.0.2 dev ntfp2 |
| $ ip addr add fd00:cafe:cafe::1/128 dev tun1 |
| $ ip link set dev tun1 up |
| $ ip route add fd00:200::/64 dev tun1 |
| $ scapy |
| >>> p = [] |
| >>> p += IPv6(src='fd00:100::1', dst='fd00:200::1')/ICMPv6EchoRequest() |
| >>> send(p, count=1, inter=0.1) |
| >>> quit() |
| $ ip -s link ls dev tun1 | grep -A1 "TX.*errors" |
| TX: bytes packets errors dropped carrier collsns |
| 0 0 1 0 0 0 |
| |
| The problem is that the network offset is set to the hard_header_len of the |
| output device (tun1, ie 14 + 20) and in our case, because the packet is |
| small (48 bytes) the pskb_inet_may_pull() fails (it tries to pull 40 bytes |
| (ipv6 header) starting from the network offset). |
| |
| This problem is more generally related to device with variable hard header |
| length. To avoid a too intrusive patch in the current release, a (ugly) |
| workaround is proposed in this patch. It has to be cleaned up in net-next. |
| |
| Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=993675a3100b1 |
| Link: http://patchwork.ozlabs.org/patch/1024489/ |
| Fixes: cb9f1b783850 ("ip: validate header length on virtual device xmit") |
| CC: Willem de Bruijn <willemb@google.com> |
| CC: Maxim Mikityanskiy <maximmi@mellanox.com> |
| Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> |
| Acked-by: Willem de Bruijn <willemb@google.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| net/packet/af_packet.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c |
| index b6ea0fadb34fa..c76c21604ffd9 100644 |
| --- a/net/packet/af_packet.c |
| +++ b/net/packet/af_packet.c |
| @@ -2887,7 +2887,8 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) |
| goto out_free; |
| } else if (reserve) { |
| skb_reserve(skb, -reserve); |
| - if (len < reserve) |
| + if (len < reserve + sizeof(struct ipv6hdr) && |
| + dev->min_header_len != dev->hard_header_len) |
| skb_reset_network_header(skb); |
| } |
| |
| -- |
| 2.19.1 |
| |