Messages in this thread | | | Subject | Re: [PATCH] af_unix: Allow Unix sockets to raise SIGURG | From | Shoaib Rao <> | Date | Fri, 29 Jan 2021 09:56:48 -0800 |
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On 1/25/21 3:36 PM, Jakub Kicinski wrote: > On Fri, 22 Jan 2021 15:06:37 +0000 Matthew Wilcox (Oracle) wrote: >> From: Rao Shoaib <rao.shoaib@oracle.com> >> >> TCP sockets allow SIGURG to be sent to the process holding the other >> end of the socket. Extend Unix sockets to have the same ability. >> >> The API is the same in that the sender uses sendmsg() with MSG_OOB to >> raise SIGURG. Unix sockets behave in the same way as TCP sockets with >> SO_OOBINLINE set. > Noob question, if we only want to support the inline mode, why don't we > require SO_OOBINLINE to have been called on @other? Wouldn't that > provide more consistent behavior across address families? > > With the current implementation the receiver will also not see MSG_OOB > set in msg->msg_flags, right?
SO_OOBINLINE does not control the delivery of signal, It controls how OOB Byte is delivered. It may not be obvious but this change does not deliver any Byte, just a signal. So, as long as sendmsg flag contains MSG_OOB, signal will be delivered just like it happens for TCP.
Shoaib
> >> SIGURG is ignored by default, so applications which do not know about this >> feature will be unaffected. In addition to installing a SIGURG handler, >> the receiving application must call F_SETOWN or F_SETOWN_EX to indicate >> which process or thread should receive the signal. >> >> Signed-off-by: Rao Shoaib <rao.shoaib@oracle.com> >> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> >> --- >> net/unix/af_unix.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c >> index 41c3303c3357..849dff688c2c 100644 >> --- a/net/unix/af_unix.c >> +++ b/net/unix/af_unix.c >> @@ -1837,8 +1837,6 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, >> return err; >> >> err = -EOPNOTSUPP; >> - if (msg->msg_flags&MSG_OOB) >> - goto out_err; >> >> if (msg->msg_namelen) { >> err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EOPNOTSUPP; >> @@ -1903,6 +1901,9 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, >> sent += size; >> } >> >> + if (msg->msg_flags & MSG_OOB) >> + sk_send_sigurg(other); >> + >> scm_destroy(&scm); >> >> return sent;
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