From 8b5a6ab3ebc9daaa473a2b700b4d6b1a1cef3bed Mon Sep 17 00:00:00 2001
From: visa <visa@openbsd.org>
Date: Mon, 25 Jul 2016 16:28:06 +0000
Subject: [PATCH] Fix rarpd hang. The receive buffer of a route socket can
 become full while rarpd process is idle. To avoid getting stuck in rtmsg(),
 the process has to clear the buffer and retry.

ok benno@ deraadt@ millert@
---
 usr.sbin/rarpd/arptab.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/usr.sbin/rarpd/arptab.c b/usr.sbin/rarpd/arptab.c
index dac132dea16..ddabb26ef22 100644
--- a/usr.sbin/rarpd/arptab.c
+++ b/usr.sbin/rarpd/arptab.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: arptab.c,v 1.26 2016/01/26 18:26:19 mmcc Exp $ */
+/*	$OpenBSD: arptab.c,v 1.27 2016/07/25 16:28:06 visa Exp $ */
 
 /*
  * Copyright (c) 1984, 1993
@@ -172,6 +172,7 @@ rtmsg(int cmd)
 	char *cp = m_rtmsg.m_space;
 	int l;
 
+retry:
 	errno = 0;
 	if (cmd == RTM_DELETE)
 		goto doit;
@@ -224,11 +225,14 @@ doit:
 		}
 	}
 	do {
-		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
+		l = recv(s, (char *)&m_rtmsg, sizeof(m_rtmsg), MSG_DONTWAIT);
 	} while (l > 0 && (rtm->rtm_version != RTM_VERSION ||
 	    rtm->rtm_seq != seq || rtm->rtm_pid != pid));
-	if (l < 0)
+	if (l < 0) {
+		if (errno == EAGAIN || errno == EINTR)
+			goto retry;
 		syslog(LOG_ERR, "arptab_set: read from routing socket: %m");
+	}
 	return (0);
 }
 
-- 
2.20.1