Date: Tue, 21 Feb 2023 17:05:53 GMT From: Gleb Smirnoff <glebius@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 71e70c25c008 - main - Revert "unix/dgram: return EAGAIN instead of ENOBUFS when O_NONBLOCK set" Message-ID: <202302211705.31LH5r2X080164@gitrepo.freebsd.org>
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The branch main has been updated by glebius: URL: https://cgit.FreeBSD.org/src/commit/?id=71e70c25c0085a4e6e5eef834ca8a29b65435d62 commit 71e70c25c0085a4e6e5eef834ca8a29b65435d62 Author: Gleb Smirnoff <glebius@FreeBSD.org> AuthorDate: 2023-02-21 16:50:07 +0000 Commit: Gleb Smirnoff <glebius@FreeBSD.org> CommitDate: 2023-02-21 16:50:07 +0000 Revert "unix/dgram: return EAGAIN instead of ENOBUFS when O_NONBLOCK set" This API change led to unexpected consequences with Go runtime. The Go runtime emulates blocking sockets over non-blocking sockets and for that uses available event dispatcher on the target OS, which is kevent(2) if availabe, with OS independent layer on top. It expects that if whatever O_NONBLOCK socket returned ever EAGAIN, then it is supposed to be reported as writable by the event dispatcher. kevent(2) would never report a unix/dgram socket, since they never change their state, they always are writeable. The expectations of Go are not literally specified by SUS, however they are in its spirit. The SUS specifies EAGAIN for send(2) as "The socket's file descriptor is marked O_NONBLOCK and the requested operation would block" [1]. This doesn't apply to FreeBSD unix/dgram socket, it never blocks on send(2). Thus, changing API trying to mimic Linux was a mistake. But what about the problem we tried to fix? Discussed that with Max Dounin of nginx, and we agreed that the log bomb described shall be fixed on nginx side, and it actually isn't specific to FreeBSD, may happen with nginx on any non-Linux system with a certain configuration. [1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/send.html This reverts commit 65572cade35a93add2168a7a012f808ac499218b. --- sys/kern/uipc_usrreq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sys/kern/uipc_usrreq.c b/sys/kern/uipc_usrreq.c index 8f86bdb48c69..294ef807416c 100644 --- a/sys/kern/uipc_usrreq.c +++ b/sys/kern/uipc_usrreq.c @@ -1338,7 +1338,7 @@ uipc_sosend_dgram(struct socket *so, struct sockaddr *addr, struct uio *uio, f = NULL; } else { soroverflow_locked(so2); - error = (so->so_state & SS_NBIO) ? EAGAIN : ENOBUFS; + error = ENOBUFS; if (f->m_next->m_type == MT_CONTROL) unp_scan(f->m_next, unp_freerights); }
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