Messages in this thread | | | Date | Fri, 4 Aug 2023 16:28:25 +0200 | From | Stefano Garzarella <> | Subject | Re: [RFC PATCH v1 1/2] vsock: send SIGPIPE on write to shutdowned socket |
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On Fri, Aug 04, 2023 at 03:46:47PM +0300, Arseniy Krasnov wrote: >Hi Stefano, > >On 02.08.2023 10:46, Stefano Garzarella wrote: >> On Tue, Aug 01, 2023 at 05:17:26PM +0300, Arseniy Krasnov wrote: >>> POSIX requires to send SIGPIPE on write to SOCK_STREAM socket which was >>> shutdowned with SHUT_WR flag or its peer was shutdowned with SHUT_RD >>> flag. Also we must not send SIGPIPE if MSG_NOSIGNAL flag is set. >>> >>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >>> --- >>> net/vmw_vsock/af_vsock.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >>> index 020cf17ab7e4..013b65241b65 100644 >>> --- a/net/vmw_vsock/af_vsock.c >>> +++ b/net/vmw_vsock/af_vsock.c >>> @@ -1921,6 +1921,9 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg, >>> err = total_written; >>> } >>> out: >>> + if (sk->sk_type == SOCK_STREAM) >>> + err = sk_stream_error(sk, msg->msg_flags, err); >> >> Do you know why we don't need this for SOCK_SEQPACKET and SOCK_DGRAM? > >Yes, here is my explanation: > >This function checks that input error is SIGPIPE, and if so it sends SIGPIPE to the 'current' thread >(except case when MSG_NOSIGNAL flag is set). This behaviour is described in POSIX: > >Page 367 (description of defines from sys/socket.h): >MSG_NOSIGNAL: No SIGPIPE generated when an attempt to send is made on a stream- >oriented socket that is no longer connected. > >Page 497 (description of SOCK_STREAM): >A SIGPIPE signal is raised if a thread sends on a broken stream (one that is >no longer connected).
Okay, but I think we should do also for SEQPACKET:
https://pubs.opengroup.org/onlinepubs/009696699/functions/xsh_chap02_10.html
In 2.10.6 Socket Types:
"The SOCK_SEQPACKET socket type is similar to the SOCK_STREAM type, and is also connection-oriented. The only difference between these types is that record boundaries ..."
Then in 2.10.14 Signals:
"The SIGPIPE signal shall be sent to a thread that attempts to send data on a socket that is no longer able to send. In addition, the send operation fails with the error [EPIPE]."
It's honestly not super clear, but I assume the problem is similar with seqpacket since it's connection-oriented, or did I miss something?
For example in sctp_sendmsg() IIUC we raise a SIGPIPE regardless of whether the socket is STREAM or SEQPACKET.
> >Page 1802 (description of 'send()' call): >MSG_NOSIGNAL > >Requests not to send the SIGPIPE signal if an attempt to >send is made on a stream-oriented socket that is no >longer connected. The [EPIPE] error shall still be >returned > >And the same for 'sendto()' and 'sendmsg()' > >Link to the POSIX document: >https://www.open-std.org/jtc1/sc22/open/n4217.pdf > >TCP (I think we must rely on it), KCM, SMC sockets (all of them are stream) work in the same >way by calling this function. AF_UNIX also works in the same way, but it implements SIGPIPE handling >without this function.
I'm okay calling this function.
> >The only thing that confused me a little bit, that sockets above returns EPIPE when >we have only SEND_SHUTDOWN set, but for AF_VSOCK EPIPE is returned for RCV_SHUTDOWN >also, but I think it is related to this patchset.
Do you mean that it is NOT related to this patchset?
Thanks, Stefano
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