FROM: Sergey Smitienko
DATE: 03/06/2001 02:01:57
SUBJECT:  http://cvs.openbsd.org/cgi-bin/wwwgnats.pl/full/1656 
>From that bug report:

>Description:
>	Under heavy load, e. g. "make build" while apache is serving (10
>Gigs/day), machine simetimes stop working. It is pingable, kernel seems to
>work, userland is gone. 

I had same troube on one of my heavy loaded OpenBSD boxes to. As far as I see
this may be caused by bug in networking code.

udp_usrreq.c: ( I removed all IPv6 code for more clearense)

/*	$OpenBSD: udp_usrreq.c,v 1.51 2000/10/13 17:58:37 itojun Exp $	*/
/*	$NetBSD: udp_usrreq.c,v 1.28 1996/03/16 23:54:03 christos Exp $	*/


int
#if __STDC__
udp_output(struct mbuf *m, ...)
#else
udp_output(m, va_alist)
	struct mbuf *m;
	va_dcl
#endif
{
	register struct inpcb *inp;
	struct mbuf *addr, *control;
	register struct udpiphdr *ui;
	register int len = m->m_pkthdr.len;
	struct in_addr laddr;
	int s = 0, error = 0;
	va_list ap;
	int pcbflags = 0;

	va_start(ap, m);
	inp = va_arg(ap, struct inpcb *);
	addr = va_arg(ap, struct mbuf *);
	control = va_arg(ap, struct mbuf *);
	va_end(ap);

	if (addr) {
	        /*
		 * Save current PCB flags because they may change during
		 * temporary connection.
		 */
                pcbflags = inp->inp_flags;

			laddr = inp->inp_laddr;
		if (inp->inp_faddr.s_addr != INADDR_ANY)
		{
			error = EISCONN;
			goto release;
		}
		/*
		 * Must block input while temporarily connected.
		 */
		s = splsoftnet();

//Here - lock networking code.

		error = in_pcbconnect(inp, addr);
		if (error) {
			splx(s);
			goto release;
		}
	} else {
		if (inp->inp_faddr.s_addr == INADDR_ANY)
		{
			error = ENOTCONN;
			goto release;
		}
	}

//At this point code my be locked, may be not.

	M_PREPEND(m, sizeof(struct udpiphdr), M_DONTWAIT);
	if (m == 0) {
		error = ENOBUFS;
		goto bail;

//Goto bail, it will splx(s) under same conditions - if (addr) { blah blah blah splx(s)}

	}


	if ((len + sizeof(struct udpiphdr)) > IP_MAXPACKET) {
		error = EMSGSIZE;

//Goto release, release does not call splx(s), but at this point code my
be locked, may be not ???

		goto release;
	}


	... blah blah blah...

	
bail:
	if (addr) {
		in_pcbdisconnect(inp);
                inp->inp_flags = pcbflags;
			inp->inp_laddr = laddr;
		splx(s);
	}
	if (control) {
		m_freem(control);
	}
	return (error);

release:
	m_freem(m);
	if (control) {
		m_freem(control);
	}
	return (error);
}

Here is my patch. It is very ugly, but my box stoped freezing.
Uptime is about a week.

udp_usrreq.c:

755c755
<       int s = 0, error = 0, is_locked = 0;
---
>       int s = 0, error = 0;
818d817
<               is_locked = 1;
822d820
<                       is_locked = 0;
993d990
<               is_locked = 0;
1002,1004d998
<
<       if ( is_locked ) splx(s);
<
1016,1018d1009
<
<       if ( is_locked ) splx(s);
<

Hope this will help.

PS. Does some one works on locale support/localisation ?
PSS. How can I became OpenBSD kernel developer, because i have some time
and I'm interested
in unix system programming.
PSSS. Sorry for my bad english.