Messages in this thread Patch in this message | | | From | Pierre Habouzit <> | Subject | [PATCH] sctp: if backlog is 0, listening shall not be deactivated. | Date | Wed, 14 Jan 2009 10:42:03 +0100 |
| |
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@intersec.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
| |