Add support for interface-mtu (option 26).

Original request+diff from matthew@

ok dlg@

4 files changed, 71 insertions, 4 deletions

diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c
index e13e1599543..4bba00a1524 100644
--- a/sbin/dhclient/dhclient.c
+++ b/sbin/dhclient/dhclient.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dhclient.c,v 1.356 2015/02/07 02:07:32 krw Exp $	*/
+/*	$OpenBSD: dhclient.c,v 1.357 2015/02/07 10:08:06 krw Exp $	*/
 
 /*
  * Copyright 2004 Henning Brauer <henning@openbsd.org>
@@ -913,6 +913,18 @@ bind_lease(void)
 	/* Deleting the addresses also clears out arp entries. */
 	delete_addresses();
 	flush_routes();
+ 
+	opt = &options[DHO_INTERFACE_MTU];
+	if (opt->len == sizeof(u_int16_t)) {
+		u_int16_t mtu;
+		memcpy(&mtu, opt->data, sizeof(mtu));
+		mtu = ntohs(mtu);
+		/* "The minimum legal value for the MTU is 68." */
+		if (mtu < 68)
+			warning("mtu size %u < 68: ignored", mtu);
+		else
+			set_interface_mtu(mtu);
+	}
 
 	opt = &options[DHO_SUBNET_MASK];
 	if (opt->len == sizeof(mask))
diff --git a/sbin/dhclient/kroute.c b/sbin/dhclient/kroute.c
index a19575a1873..98d624159c8 100644
--- a/sbin/dhclient/kroute.c
+++ b/sbin/dhclient/kroute.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kroute.c,v 1.72 2015/02/07 02:07:32 krw Exp $	*/
+/*	$OpenBSD: kroute.c,v 1.73 2015/02/07 10:08:06 krw Exp $	*/
 
 /*
  * Copyright 2012 Kenneth R Westerback <krw@openbsd.org>
@@ -364,6 +364,47 @@ priv_delete_address(struct imsg_delete_address *imsg)
 }
 
 /*
+ * [priv_]set_interface_mtu is the equivalent of
+ *
+ *      ifconfig <if> mtu <mtu>
+ */
+void
+set_interface_mtu(int mtu)
+{
+	struct imsg_set_interface_mtu imsg;
+	int rslt;
+
+	memset(&imsg, 0, sizeof(imsg));
+
+	imsg.mtu = mtu;
+
+	rslt = imsg_compose(unpriv_ibuf, IMSG_SET_INTERFACE_MTU, 0, 0, -1,
+	    &imsg, sizeof(imsg));
+	if (rslt == -1)
+		warning("set_interface_mtu: imsg_compose: %s", strerror(errno));
+
+	flush_unpriv_ibuf("set_interface_mtu");
+}
+
+void
+priv_set_interface_mtu(struct imsg_set_interface_mtu *imsg)
+{
+	struct ifreq ifr;
+	int s;
+
+	memset(&ifr, 0, sizeof(ifr));
+
+	strlcpy(ifr.ifr_name, ifi->name, sizeof(ifr.ifr_name));
+	ifr.ifr_mtu = imsg->mtu;
+
+	if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1)
+		error("socket open failed: %s", strerror(errno));
+	if (ioctl(s, SIOCSIFMTU, &ifr) < 0)
+		warning("SIOCSIFMTU failed (%d): %s", imsg->mtu, strerror(errno));
+	close(s);
+}
+
+/*
  * [priv_]add_address is the equivalent of
  *
  *	ifconfig <if> inet <addr> netmask <mask> broadcast <addr>
diff --git a/sbin/dhclient/privsep.c b/sbin/dhclient/privsep.c
index 56f83ea2764..3c0b5203b9f 100644
--- a/sbin/dhclient/privsep.c
+++ b/sbin/dhclient/privsep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: privsep.c,v 1.38 2015/02/06 09:16:06 reyk Exp $ */
+/*	$OpenBSD: privsep.c,v 1.39 2015/02/07 10:08:06 krw Exp $ */
 
 /*
  * Copyright (c) 2004 Henning Brauer <henning@openbsd.org>
@@ -69,6 +69,14 @@ dispatch_imsg(struct imsgbuf *ibuf)
 				priv_add_route(imsg.data);
 			break;
 
+		case IMSG_SET_INTERFACE_MTU:
+			if (imsg.hdr.len != IMSG_HEADER_SIZE +
+			    sizeof(struct imsg_set_interface_mtu))
+				warning("bad IMSG_SET_INTERFACE_MTU");
+			else
+				priv_set_interface_mtu(imsg.data);
+			break;
+
 		case IMSG_HUP:
 			if (imsg.hdr.len != IMSG_HEADER_SIZE +
 			    sizeof(struct imsg_hup))
diff --git a/sbin/dhclient/privsep.h b/sbin/dhclient/privsep.h
index a394fe02fcf..34bcb64cd3a 100644
--- a/sbin/dhclient/privsep.h
+++ b/sbin/dhclient/privsep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: privsep.h,v 1.26 2015/02/06 09:16:06 reyk Exp $ */
+/*	$OpenBSD: privsep.h,v 1.27 2015/02/07 10:08:06 krw Exp $ */
 
 /*
  * Copyright (c) 2004 Henning Brauer <henning@openbsd.org>
@@ -26,6 +26,7 @@ enum imsg_code {
 	IMSG_ADD_ADDRESS,
 	IMSG_FLUSH_ROUTES,
 	IMSG_ADD_ROUTE,
+	IMSG_SET_INTERFACE_MTU,
 	IMSG_HUP,
 	IMSG_WRITE_RESOLV_CONF,
 	IMSG_WRITE_OPTION_DB
@@ -52,6 +53,10 @@ struct imsg_add_route {
 	int		flags;
 };
 
+struct imsg_set_interface_mtu {
+	int	mtu;
+};
+
 struct imsg_hup {
 	struct	in_addr addr;
 };
@@ -62,6 +67,7 @@ void	priv_add_address(struct imsg_add_address *);
 void	priv_flush_routes(struct imsg_flush_routes *);
 void	priv_add_route(struct imsg_add_route *);
 void	priv_cleanup(struct imsg_hup *);
+void	priv_set_interface_mtu(struct imsg_set_interface_mtu *);
 void	priv_write_resolv_conf(struct imsg *);
 void	priv_write_option_db(struct imsg *);
 void	priv_write_file(char *, int, mode_t, uid_t, gid_t, u_int8_t *, size_t);