On Mon, Mar 21, 2022 at 10:42:05AM +0100, Pablo Neira Ayuso wrote:
> When tcp_options is called all flags are cleared.
> When the IP_CT_TCP_FLAG_BE_LIBERAL is set it should be preserved
> otherwise such connections will fail in the window check.
This patch completes 8437a6209f76 ("netfilter: nft_flow_offload: set liberal tracking mode for tcp")
I'm going to send v2 to add a wrapper function to update these flags,
so we do not accidentally reset IP_CT_TCP_FLAG_BE_LIBERAL.
> Signed-off-by: Sven Auhagen <sven.auhagen@xxxxxxxxxxxx>
> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> ---
> Supersedes: https://patchwork.ozlabs.org/project/netfilter-devel/patch/20220318144939.69465-1-pablo@xxxxxxxxxxxxx/ which is not correct, it breaks TCP FIN handling.
>
> net/netfilter/nf_conntrack_proto_tcp.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
> index d1582b888c0d..d8599ab5f767 100644
> --- a/net/netfilter/nf_conntrack_proto_tcp.c
> +++ b/net/netfilter/nf_conntrack_proto_tcp.c
> @@ -342,7 +342,7 @@ static void tcp_options(const struct sk_buff *skb,
> return;
>
> state->td_scale =
> - state->flags = 0;
> + state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL;
>
> while (length > 0) {
> int opcode=*ptr++;
> @@ -873,7 +873,7 @@ int nf_conntrack_tcp_packet(struct nf_conn *ct,
> struct nf_tcp_net *tn = nf_tcp_pernet(net);
> struct nf_conntrack_tuple *tuple;
> enum tcp_conntrack new_state, old_state;
> - unsigned int index, *timeouts;
> + unsigned int index, flags, *timeouts;
> enum ip_conntrack_dir dir;
> const struct tcphdr *th;
> struct tcphdr _tcph;
> @@ -968,8 +968,10 @@ int nf_conntrack_tcp_packet(struct nf_conn *ct,
> ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
> ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
> ct->proto.tcp.last_flags;
> + flags = ct->proto.tcp.seen[dir].flags;
> memset(&ct->proto.tcp.seen[dir], 0,
> sizeof(struct ip_ct_tcp_state));
> + ct->proto.tcp.seen[dir].flags = flags & IP_CT_TCP_FLAG_BE_LIBERAL;
> break;
> }
> ct->proto.tcp.last_index = index;
> --
> 2.30.2
>
