On 04.08.2023 18:02, Stefano Garzarella wrote: > On Fri, Aug 04, 2023 at 05:34:20PM +0300, Arseniy Krasnov wrote: >> >> >> On 04.08.2023 17:28, Stefano Garzarella wrote: >>> 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@xxxxxxxxxxxxxx> >>>>>> --- >>>>>> 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. >> >> Hm, yes, you're right. Seems check for socket type is not needed in this case, >> as this function is only for connection oriented sockets. > > Ack! > >> >>> >>>> >>>> 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? >> >> Yes, **NOT** > > Got it, so if you have time when you're back, let's check also that > (not for this series as you mentioned). ^^^ Hello Stefano, so: there is some confusion with check for RCV_SHUTDOWN: it presents in AF_UNIX, but missed in TCP (it checks only for SEND_SHUTDOWN). I performed simple test which tries to send data to peer which already called shutdown(SHUT_RD) - AF_UNIX and TCP behave differently. AF_UNIX sends SIGPIPE, while TCP allows to send data. I suggest to not touch this check for AF_VSOCK (e.g. continue work as AF_UNIX), because I don't see strong motivation/argument to remove it. Thanks, Arseniy > > Thanks, > Stefano >
