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tcp: add skb-less helpers to retrieve SYN cookie

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This patch allows generation of a SYN cookie before an SKB has been
allocated, as is the case at XDP.

Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Petar Penkov 2019-07-29 09:59:14 -07:00 • committed by Alexei Starovoitov
parent 965112785e
commit 9349d600fb
4 changed files with 113 additions and 0 deletions
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15
net/ipv4/tcp_ipv4.c
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@ -1515,6 +1515,21 @@ static struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb)
return sk;
}
u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
struct tcphdr *th, u32 *cookie)
{
u16 mss = 0;
#ifdef CONFIG_SYN_COOKIES
mss = tcp_get_syncookie_mss(&tcp_request_sock_ops,
&tcp_request_sock_ipv4_ops, sk, th);
if (mss) {
*cookie = __cookie_v4_init_sequence(iph, th, &mss);
tcp_synq_overflow(sk);
}
#endif
return mss;
}
/* The socket must have it's spinlock held when we get
* here, unless it is a TCP_LISTEN socket.
*