From 0a26f85822741c8f0c3a3008df437aabf0e59e67 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Wed, 22 Aug 2012 13:53:37 +0000
Subject: [PATCH] Revert r239356 and use an alternate algorithm.

First, don't exit when the link goes down on an interface.  Instead,
teach dhclient to track changes in link state and to enter the reboot
state when the link on an interface goes up causing dhclient to attempt
to renew its existing lease.

Second, remove the change I added to clear the old lease when dhclient
exits due to an error (such as ifconfig down).  If an interface is
using autoconfiguration it should keep its autoconfiguration as much as
possible.  If the next time it needs a configuration it is able to reuse
the previous autoconfiguration, then leaving the settings intact allows
existing connections to survive temporary outages, etc.

PR:		bin/166656
MFC after:	1 month
---
 sbin/dhclient/dhclient.c | 16 ++++++++++------
 sbin/dhclient/dhcpd.h    |  1 +
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c
index 7260d3f21e19..f71c8c836050 100644
--- a/sbin/dhclient/dhclient.c
+++ b/sbin/dhclient/dhclient.c
@@ -218,6 +218,7 @@ routehandler(struct protocol *p)
 	struct sockaddr *sa;
 	struct iaddr a;
 	ssize_t n;
+	int linkstat;
 
 	n = read(routefd, &msg, sizeof(msg));
 	rtm = (struct rt_msghdr *)msg;
@@ -278,10 +279,14 @@ routehandler(struct protocol *p)
 			    ifi->name);
 			goto die;
 		}
-		if (!interface_link_status(ifi->name)) {
-			warning("Interface %s is down, dhclient exiting",
-			    ifi->name);
-			goto die;
+		linkstat = interface_link_status(ifi->name);
+		if (linkstat != ifi->linkstat) {
+			debug("%s link state %s -> %s", ifi->name,
+			    ifi->linkstat ? "up" : "down",
+			    linkstat ? "up" : "down");
+			ifi->linkstat = linkstat;
+			if (linkstat)
+				state_reboot(ifi);
 		}
 		break;
 	case RTM_IFANNOUNCE:
@@ -321,8 +326,6 @@ routehandler(struct protocol *p)
 
 die:
 	script_init("FAIL", NULL);
-	if (ifi->client->active)
-		script_write_params("old_", ifi->client->active);
 	if (ifi->client->alias)
 		script_write_params("alias_", ifi->client->alias);
 	script_go();
@@ -437,6 +440,7 @@ main(int argc, char *argv[])
 		}
 		fprintf(stderr, " got link\n");
 	}
+	ifi->linkstat = 1;
 
 	if ((nullfd = open(_PATH_DEVNULL, O_RDWR, 0)) == -1)
 		error("cannot open %s: %m", _PATH_DEVNULL);
diff --git a/sbin/dhclient/dhcpd.h b/sbin/dhclient/dhcpd.h
index 1334a7c4a055..4762cbd05f86 100644
--- a/sbin/dhclient/dhcpd.h
+++ b/sbin/dhclient/dhcpd.h
@@ -208,6 +208,7 @@ struct interface_info {
 	int			 errors;
 	int			 dead;
 	u_int16_t		 index;
+	int			 linkstat;
 };
 
 struct timeout {