netdev - Re: [net-next-2.6 PATCH v6 4/7 RFC] TCPCT part 1d: define TCP cookie option, extend existing struct's

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Date:	Wed, 18 Nov 2009 08:55:48 -0500
From:	William Allen Simpson <william.allen.simpson@...il.com>
To:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Joe Perches <joe@...ches.com>,
	David Miller <davem@...emloft.net>
Subject: Re: [net-next-2.6 PATCH v6 4/7 RFC] TCPCT part 1d: define TCP cookie
 option, extend existing struct's

Ilpo Järvinen wrote:
> You both are right (and that's what is causing confusion)...
> 
In this case, for /this/ code, *none* of you are correct, and _that's_
causing confusion.  There is no independent retransmission of SYNACK data!
None!!  Nada!!!  There is no retransmission queue for SYNACK data.

SYN with SACK should never be sent, and should never be received -- and
already should be discarded and ignored (outside the scope of this patch).

As I've already mentioned in this thread 2 days ago, in my earlier patches
(now deferred to part 2 after the functional split requested by Eric and
Ilpo), the request_sock was removed entirely (just like syncookies).
There wasn't (and won't be) any struct or timer lying around to allow
SYNACK data retransmissions to occur.

Even now, the entire s_data_* edifice isn't passed to be retransmitted.
Note the code (in part 1a), already reviewed and Ack'd:

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 4be2228..7a42990 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -537,7 +537,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
  		 * Enforce "SYN-ACK" according to figure 8, figure 6
  		 * of RFC793, fixed by RFC1122.
  		 */
-		req->rsk_ops->rtx_syn_ack(sk, req);
+		req->rsk_ops->rtx_syn_ack(sk, req, NULL);
  		return NULL;
  	}

See that NULL?  There's no cookie data structure for retransmission!

Could we end this diversion into rampant speculation?
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