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Date: Thu, 12 Apr 2018 20:39:40 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Re: [PATCH] add SOCK_STREAM support for syslog
On Thu, Apr 12, 2018 at 03:04:31PM +0200, Hrvoje Varga wrote:
> > To be consistent with glibc and uClibc since both glibc and uClibc
> > have a support for connecting to SOCK_STREAM socket in case
> > when connection to a SOCK_DGRAM is unsuccessful. This patch mimics the
> > same behavior.
> >
> > There was a discussion whether the musl should support the SOCK_STREAM
> > on musl mailing list http://www.openwall.com/lists/musl/2015/08/10/1.
Yes, and it never really concluded. I think it's probably harmless to
support SOCK_STREAM if users want it though. But the patch is probably
insufficient.
One question I had that never got answered: are SOCK_DGRAM and
SOCK_STREAM unix socket addresses mutually exclusive, or can the same
name be listening as both types? This affects how we handle certain
error cases I think..
> > Signed-off-by: Hrvoje Varga <hrvoje.varga@...tura.hr>
> > ---
> > src/misc/syslog.c | 18 ++++++++++++++++--
> > 1 file changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/misc/syslog.c b/src/misc/syslog.c
> > index 9dd1ddb5..101847a4 100644
> > --- a/src/misc/syslog.c
> > +++ b/src/misc/syslog.c
> > @@ -48,8 +48,22 @@ void closelog(void)
> >
> > static void __openlog()
> > {
> > - log_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0);
> > - if (log_fd >= 0) connect(log_fd, (void *)&log_addr, sizeof log_addr);
> > + int retry = 0;
> > + int sock_type = SOCK_DGRAM;
> > + while (retry < 2) {
> > + retry++;
> > + log_fd = socket(AF_UNIX, sock_type|SOCK_CLOEXEC, 0);
> > + if (log_fd >= 0) {
> > + if (connect(log_fd, (void *)&log_addr, sizeof log_addr) != -1) {
> > + return;
> > + }
> > + if (errno == EPROTOTYPE) {
> > + sock_type = SOCK_STREAM;
> > + }
> > + close(log_fd);
> > + log_fd = -1;
> > + }
> > + }
> > }
> >
> > void openlog(const char *ident, int opt, int facility)
This only covers opening, not reconnection on loss, which happens in
_vsyslog. The way reconnection would have to be handled for
SOCK_STREAM is different and less robust, I think, so we probably
can't just replace the existing code but would need a new code path
for it.
Rich
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