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.
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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