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Message-Id: <1231926123-26196-1-git-send-email-pierre.habouzit@intersec.com>
Date: Wed, 14 Jan 2009 10:42:03 +0100
From: Pierre Habouzit <pierre.habouzit@...ersec.com>
To: Wei Yongjun <yjwei@...fujitsu.com>,
Vlad Yasevich <vladislav.yasevich@...com>,
" David S. Miller" <davem@...emloft.net>
Cc: linux-kernel@...r.kernel.org,
Pierre Habouzit <pierre.habouzit@...ersec.com>
Subject: [PATCH] sctp: if backlog is 0, listening shall not be deactivated.
POSIX hints that when 0 is used for the listen backlog argument, the
kernel shall chose a default automatic value. TCP for example, works this
way.
Signed-off-by: Pierre Habouzit <pierre.habouzit@...ersec.com>
---
net/sctp/socket.c | 20 --------------------
1 files changed, 0 insertions(+), 20 deletions(-)
To put a bit of background, I stumbled against this while doing a code
that basically did:
struct sctp_event_subscribe events;
/* ... */
fd = socket(AF_INET, SOCK_SEQPACKETS, IPPROTO_SCTP);
sctp_bindx(fd, ....);
events = (struct sctp_event_subscribe){
.sctp_data_io_event = 1,
.sctp_association_event = 1,
};
setsockopt(fd, SOL_SCTP, SCTP_EVENTS, &events, sizeof(events));
listen(fd, 0);
len = sctp_recvmsg(fd, .....);
The latter call instead of blocking like I expected returned with
errno == ENOTCONN.
I know POSIX doesn't _require_ listen() to accept 0 as a valid backlog,
but the other listen() implementation I have used in the kernel do, and
it looks really surprising for the programmer (who really searches the
error elsewhere).
Fortunately I had another working code at hand and I managed to find the
problem resorting to reverting the changes I made to the original code
line per line (*sigh*).
I'm unsure if the diff shouldn't do instead:
if (!backlog)
backlog = 1;
I'm not really comfortable around the kernel core ;)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index ff0a8f8..da1d96a 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5866,16 +5866,6 @@ SCTP_STATIC int sctp_seqpacket_listen(struct sock *sk, int backlog)
if (!sctp_style(sk, UDP))
return -EINVAL;
- /* If backlog is zero, disable listening. */
- if (!backlog) {
- if (sctp_sstate(sk, CLOSED))
- return 0;
-
- sctp_unhash_endpoint(ep);
- sk->sk_state = SCTP_SS_CLOSED;
- return 0;
- }
-
/* Return if we are already listening. */
if (sctp_sstate(sk, LISTENING))
return 0;
@@ -5919,16 +5909,6 @@ SCTP_STATIC int sctp_stream_listen(struct sock *sk, int backlog)
struct sctp_sock *sp = sctp_sk(sk);
struct sctp_endpoint *ep = sp->ep;
- /* If backlog is zero, disable listening. */
- if (!backlog) {
- if (sctp_sstate(sk, CLOSED))
- return 0;
-
- sctp_unhash_endpoint(ep);
- sk->sk_state = SCTP_SS_CLOSED;
- return 0;
- }
-
if (sctp_sstate(sk, LISTENING))
return 0;
--
1.6.1.161.g5e07b.dirty
--
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