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Subject[PATCH v3 5/7] TCPCT part 2e: accept SYNACK data
When accompanied by cookie option, Initiator (client) queues incoming
SYNACK transaction data.

This is a straightforward re-implementation of an earlier (year-old)
patch that no longer applies cleanly, with permission of the original
author (Adam Langley). The patch was previously reviewed:

http://thread.gmane.org/gmane.linux.network/102586

This function will also be used in subsequent patches that implement
additional features.

Requires:
TCPCT part 1g: Responder Cookie => Initiator
net: tcp_header_len_th and tcp_option_len_th

Signed-off-by: William.Allen.Simpson@gmail.com
---
net/ipv4/tcp_input.c | 26 +++++++++++++++++++++++++-
1 files changed, 25 insertions(+), 1 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8e0f6ae..165040e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5395,6 +5395,12 @@ discard:
return 0;
}

+/*
+ * Returns:
+ * +1 on reset,
+ * 0 success and/or SYNACK data,
+ * -1 on discard.
+ */
static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
struct tcphdr *th)
{
@@ -5403,6 +5409,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
struct tcp_sock *tp = tcp_sk(sk);
struct tcp_cookie_values *cvp = tp->cookie_values;
int saved_clamp = tp->rx_opt.mss_clamp;
+ int queued = 0;

tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0);

@@ -5509,6 +5516,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
- TCPOLEN_COOKIE_BASE;
int cookie_pair_size = cookie_size
+ cvp->cookie_desired;
+ int tcp_header_len = tcp_header_len_th(th);

/* A cookie extension option was sent and returned.
* Note that each incoming SYNACK replaces the
@@ -5524,6 +5532,19 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
hash_location, cookie_size);
cvp->cookie_pair_size = cookie_pair_size;
}
+
+ queued = skb->len - tcp_header_len;
+ if (queued > 0) {
+ /* Queue incoming transaction data. */
+ __skb_pull(skb, tcp_header_len);
+ __skb_queue_tail(&sk->sk_receive_queue, skb);
+ skb_set_owner_r(skb, sk);
+ sk->sk_data_ready(sk, 0);
+ cvp->s_data_in = 1; /* true */
+ tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+ tp->rcv_wup = TCP_SKB_CB(skb)->end_seq;
+ tp->copied_seq = TCP_SKB_CB(skb)->seq + 1;
+ }
}

smp_mb();
@@ -5577,11 +5598,14 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
TCP_DELACK_MAX, TCP_RTO_MAX);

discard:
- __kfree_skb(skb);
+ if (queued <= 0)
+ __kfree_skb(skb);
return 0;
} else {
tcp_send_ack(sk);
}
+ if (queued > 0)
+ return 0;
return -1;
}

--
1.6.3.3
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