linux-kernel - [PATCH 1/2] tcp: allow to enable repair mode for sockets in closing states

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Message-Id: <1397161539-27804-2-git-send-email-avagin@openvz.org>
Date:	Fri, 11 Apr 2014 00:25:38 +0400
From:	Andrey Vagin <avagin@...nvz.org>
To:	linux-kernel@...r.kernel.org
Cc:	criu@...nvz.org, netdev@...r.kernel.org,
	Andrey Vagin <avagin@...nvz.org>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: [PATCH 1/2] tcp: allow to enable repair mode for sockets in closing states

The repair mode is used for dumping state of tcp connections
(sequence numbers, queues, options, etc).

Currently the repair mode can be enalbed only for sockets in the
TCP_ESTABLISHED state. If a socket in another state, its internal
state can not be dumped.

Same time there is no guarantee that a connection won't be in other
states when we are dumping it, thus to be able to dump and restore
such states we need to get rid of CLOSE,ESTABLISHED in-kernel
limitation.

I see nothing wrong to allow enabling of the repair mode for connected
sockets in any states.

Cc: "David S. Miller" <davem@...emloft.net>
Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>
Cc: James Morris <jmorris@...ei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Cc: Patrick McHardy <kaber@...sh.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Cyrill Gorcunov <gorcunov@...nvz.org>
Signed-off-by: Andrey Vagin <avagin@...nvz.org>
---
 net/ipv4/tcp.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2c7e326..bcb1d59 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1106,15 +1106,18 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	}
 
 	if (unlikely(tp->repair)) {
+		err = -EINVAL;
+		if (tp->repair_queue == TCP_NO_QUEUE)
+			goto out_err;
+
+		if (sk->sk_state != TCP_ESTABLISHED)
+			goto out_err;
+
 		if (tp->repair_queue == TCP_RECV_QUEUE) {
 			copied = tcp_send_rcvq(sk, msg, size);
 			goto out;
 		}
 
-		err = -EINVAL;
-		if (tp->repair_queue == TCP_NO_QUEUE)
-			goto out_err;
-
 		/* 'common' sending to sendq */
 	}
 
@@ -2375,7 +2378,8 @@ void tcp_sock_destruct(struct sock *sk)
 static inline bool tcp_can_repair_sock(const struct sock *sk)
 {
 	return ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN) &&
-		((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_ESTABLISHED));
+		!((1 << sk->sk_state) & (TCPF_LISTEN |
+					 TCPF_SYN_SENT | TCPF_SYN_RECV));
 }
 
 static int tcp_repair_options_est(struct tcp_sock *tp,
-- 
1.9.0

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