Hey Maxim,
On 3/29/22 3:30 PM, Maxim Mikityanskiy wrote:
bpf_tcp_gen_syncookie looks at the IP version in the IP header and
validates the address family of the socket. It supports IPv4 packets in
AF_INET6 dual-stack sockets.
On the other hand, bpf_tcp_check_syncookie looks only at the address
family of the socket, ignoring the real IP version in headers, and
validates only the packet size. This implementation has some drawbacks:
1. Packets are not validated properly, allowing a BPF program to trick
bpf_tcp_check_syncookie into handling an IPv6 packet on an IPv4
socket.
2. Dual-stack sockets fail the checks on IPv4 packets. IPv4 clients end
up receiving a SYNACK with the cookie, but the following ACK gets
dropped.
This patch fixes these issues by changing the checks in
bpf_tcp_check_syncookie to match the ones in bpf_tcp_gen_syncookie. IP
version from the header is taken into account, and it is validated
properly with address family.
Fixes: 399040847084 ("bpf: add helper to check for a valid SYN cookie")
Signed-off-by: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
Could you do one final spin (while retaining Arthur's Ack) by splitting
off the selftest into a separate commit? Otherwise stable folks likely
won't be able to pick the fix up. Otherwise lgtm.
Thanks,
Daniel
