On Fri, Jan 11, 2019 at 9:44 AM Nicolas Dichtel <nicolas.dich...@6wind.com> wrote: > > 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). Let's reset the network > offset so that it points to the beginning of the L3 data, ie skb->data.
This only just landed in my inbox, sorry for the delay. So far I'm not reproducing the issue, but I'm trying and am having a look. Which pskb_inet_may_pull() is failing?
