4.20-stable review patch. If anyone has any objections, please let me know.
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[ 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/?i... 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 d0945253f43b3..3b1a78906bc0c 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); }