On 22.08.2023 12:39, Stefano Garzarella wrote: > On Mon, Aug 14, 2023 at 10:46:05PM +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. >> >> Update about sending SIGPIPE for SOCK_SEQPACKET, I checked POSIX doc and kernel sources more deeply: >> >> >> 1) >> >> I checked four types of sockets, which sends SIGPIPE for SOCK_SEQPACKET or not ('YES' if >> this socket sends SIGPIPE in SOCK_SEQPACKET case): >> >> net/kcm/: YES >> net/unix/: NO >> net/sctp/: YES >> net/caif/: NO >> >> Looking for this, I think it is impossible to get the right answer, as there is some >> mess - everyone implements it as wish. > > Eheh, I had the same impression! > >> >> 2) >> >> I opened POSIX spec again, and here are details about returning EPIPE from pages >> for 'send()', 'sendto()', 'sendmsg()': >> >> [EPIPE] The socket is shut down for writing, or the socket is connection-mode and is >> no longer connected. In the latter case, and if the socket is of type >> SOCK_STREAM, the SIGPIPE signal is generated to the calling thread >> >> So my opinion is that we need to send SIGPIPE only for SOCK_STREAM. Another question >> is how to interpret this from above (but again - SIGPIPE is related for SOCK_STREAM >> only): >> >> **" and is no longer connected"** >> >> IIUC, if we follow POSIX strictly, this check must be like: >> >> /* socket is shut down for writing or no longer connected. */ >> if (sk->sk_shutdown & SEND_SHUTDOWN || >> vsk->peer_shutdown & RCV_SHUTDOWN || >> sock_flag(SOCK_DONE)) { >> err = -EPIPE; >> goto out; >> } >> >> ... >> >> out: >> /* Handle -EPIPE for stream socket which is no longer connected. */ >> if (sk->sk_type == SOCK_STREAM && >> sock_flag(SOCK_DONE)) >> err = sk_stream_error(); >> >> >> >> From the other side, we can just follow TCP/AF_UNIX implementations as both are >> popular types of socket. In this case I suggest to implement this check like >> (e.g. without sock_flag(SOCK_DONE)): >> >> >> if (sk->sk_shutdown & SEND_SHUTDOWN || >> vsk->peer_shutdown & RCV_SHUTDOWN) { >> err = -EPIPE; >> goto out; >> } >> >> ... >> >> out: >> if (sk->sk_type == SOCK_STREAM) >> err = sk_stream_error(); >> >> What do you think? > > I'd follow TCP/AF_UNIX implementations, but it is up to you ;-) Got it, I'll use this approach Thanks, Arseniy > > Thanks, > Stefano >
