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BACKPORT: tcp: bpf: Optionally store mac header in TCP_SAVE_SYN

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This patch is adapted from Eric's patch in an earlier discussion [1].

The TCP_SAVE_SYN currently only stores the network header and
tcp header.  This patch allows it to optionally store
the mac header also if the setsockopt's optval is 2.

It requires one more bit for the "save_syn" bit field in tcp_sock.
This patch achieves this by moving the syn_smc bit next to the is_mptcp.
The syn_smc is currently used with the TCP experimental option.  Since
syn_smc is only used when CONFIG_SMC is enabled, this patch also puts
the "IS_ENABLED(CONFIG_SMC)" around it like the is_mptcp did
with "IS_ENABLED(CONFIG_MPTCP)".

The mac_hdrlen is also stored in the "struct saved_syn"
to allow a quick offset from the bpf prog if it chooses to start
getting from the network header or the tcp header.

[1]: https://lore.kernel.org/netdev/CANn89iLJNWh6bkH7DNhy_kmcAexuUCccqERqe7z2QsvPhGrYPQ@mail.gmail.com/

Suggested-by: Eric Dumazet <[email protected]>
Change-Id: Ib5dd358e17dbc89275dbbdef4eff1fb9fc2c318c
Signed-off-by: Martin KaFai Lau <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
This commit is contained in:
Martin KaFai Lau 2020-08-20 12:01:23 -07:00 • committed by basamaryan
commit b9aaf9a4a6
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7 changed files with 48 additions and 12 deletions
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3
net/ipv4/tcp.c
View file

@ -3103,7 +3103,8 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
break;
case TCP_SAVE_SYN:
if (val < 0 || val > 1)
/* 0: disable, 1: enable, 2: start from ether_header */
if (val < 0 || val > 2)
err = -EINVAL;
else
tp->save_syn = val;

14
net/ipv4/tcp_input.c
View file

@ -6723,13 +6723,25 @@ static void tcp_reqsk_record_syn(const struct sock *sk,
if (tcp_sk(sk)->save_syn) {
u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb);
struct saved_syn *saved_syn;
u32 mac_hdrlen;
void *base;
if (tcp_sk(sk)->save_syn == 2) { /* Save full header. */
base = skb_mac_header(skb);
mac_hdrlen = skb_mac_header_len(skb);
len += mac_hdrlen;
} else {
base = skb_network_header(skb);
mac_hdrlen = 0;
}
saved_syn = kmalloc(struct_size(saved_syn, data, len),
GFP_ATOMIC);
if (saved_syn) {
saved_syn->mac_hdrlen = mac_hdrlen;
saved_syn->network_hdrlen = skb_network_header_len(skb);
saved_syn->tcp_hdrlen = tcp_hdrlen(skb);
memcpy(saved_syn->data, skb_network_header(skb), len);
memcpy(saved_syn->data, base, len);
req->saved_syn = saved_syn;
}
}