Commit 9643f455 authored by Chris Friesen's avatar Chris Friesen Committed by David S. Miller
Browse files

ipv4: teach ipconfig about the MTU option in DHCP 



The DHCP spec allows the server to specify the MTU.  This can be useful
for netbooting with UDP-based NFS-root on a network using jumbo frames.
This patch allows the kernel IP autoconfiguration to handle this option
correctly.

It would be possible to use initramfs and add a script to set the MTU,
but that seems like a complicated solution if no initramfs is otherwise
necessary, and would bloat the kernel image more than this code would.

This patch was originally submitted to LKML in 2003 by Hans-Peter Jansen.

Signed-off-by: default avatarChris Friesen <cfriesen@nortel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fd2120ca

net/ipv4/ipconfig.c

+37 −4
Original line number Diff line number Diff line
@@ -160,6 +160,9 @@ static char user_dev_name[IFNAMSIZ] __initdata = { 0, }; 
/* Protocols supported by available interfaces */

static int ic_proto_have_if __initdata = 0;



/* MTU for boot device */

static int ic_dev_mtu __initdata = 0;



#ifdef IPCONFIG_DYNAMIC

static DEFINE_SPINLOCK(ic_recv_lock);

static volatile int ic_got_reply __initdata = 0;    /* Proto(s) that replied */
@@ -286,7 +289,7 @@ set_sockaddr(struct sockaddr_in *sin, __be32 addr, __be16 port) 
	sin->sin_port = port;

}



static int __init ic_dev_ioctl(unsigned int cmd, struct ifreq *arg)

static int __init ic_devinet_ioctl(unsigned int cmd, struct ifreq *arg)

{

	int res;
@@ -297,6 +300,17 @@ static int __init ic_dev_ioctl(unsigned int cmd, struct ifreq *arg) 
	return res;

}



static int __init ic_dev_ioctl(unsigned int cmd, struct ifreq *arg)

{

	int res;



	mm_segment_t oldfs = get_fs();

	set_fs(get_ds());

	res = dev_ioctl(&init_net, cmd, (struct ifreq __user *) arg);

	set_fs(oldfs);

	return res;

}



static int __init ic_route_ioctl(unsigned int cmd, struct rtentry *arg)

{

	int res;
@@ -321,20 +335,31 @@ static int __init ic_setup_if(void) 
	memset(&ir, 0, sizeof(ir));

	strcpy(ir.ifr_ifrn.ifrn_name, ic_dev->name);

	set_sockaddr(sin, ic_myaddr, 0);

	if ((err = ic_dev_ioctl(SIOCSIFADDR, &ir)) < 0) {

	if ((err = ic_devinet_ioctl(SIOCSIFADDR, &ir)) < 0) {

		printk(KERN_ERR "IP-Config: Unable to set interface address (%d).\n", err);

		return -1;

	}

	set_sockaddr(sin, ic_netmask, 0);

	if ((err = ic_dev_ioctl(SIOCSIFNETMASK, &ir)) < 0) {

	if ((err = ic_devinet_ioctl(SIOCSIFNETMASK, &ir)) < 0) {

		printk(KERN_ERR "IP-Config: Unable to set interface netmask (%d).\n", err);

		return -1;

	}

	set_sockaddr(sin, ic_myaddr | ~ic_netmask, 0);

	if ((err = ic_dev_ioctl(SIOCSIFBRDADDR, &ir)) < 0) {

	if ((err = ic_devinet_ioctl(SIOCSIFBRDADDR, &ir)) < 0) {

		printk(KERN_ERR "IP-Config: Unable to set interface broadcast address (%d).\n", err);

		return -1;

	}

	/* Handle the case where we need non-standard MTU on the boot link (a network

	 * using jumbo frames, for instance).  If we can't set the mtu, don't error

	 * out, we'll try to muddle along.

	 */

	if (ic_dev_mtu != 0) {

		strcpy(ir.ifr_name, ic_dev->name);

		ir.ifr_mtu = ic_dev_mtu;

		if ((err = ic_dev_ioctl(SIOCSIFMTU, &ir)) < 0)

			printk(KERN_ERR "IP-Config: Unable to set interface mtu to %d (%d).\n",

			                 ic_dev_mtu, err);

	}

	return 0;

}
@@ -623,6 +648,7 @@ ic_dhcp_init_options(u8 *options) 
			12,	/* Host name */

			15,	/* Domain name */

			17,	/* Boot path */

			26,	/* MTU */

			40,	/* NIS domain name */

		};
@@ -798,6 +824,7 @@ static void __init ic_do_bootp_ext(u8 *ext) 
{

       u8 servers;

       int i;

	u16 mtu;



#ifdef IPCONFIG_DEBUG

	u8 *c;
@@ -837,6 +864,10 @@ static void __init ic_do_bootp_ext(u8 *ext) 
			if (!root_server_path[0])

				ic_bootp_string(root_server_path, ext+1, *ext, sizeof(root_server_path));

			break;

		case 26:	/* Interface MTU */

			memcpy(&mtu, ext+1, sizeof(mtu));

			ic_dev_mtu = ntohs(mtu);

			break;

		case 40:	/* NIS Domain name (_not_ DNS) */

			ic_bootp_string(utsname()->domainname, ext+1, *ext, __NEW_UTS_LEN);

			break;
@@ -1403,6 +1434,8 @@ static int __init ip_auto_config(void) 
	printk(",\n     bootserver=%pI4", &ic_servaddr);

	printk(", rootserver=%pI4", &root_server_addr);

	printk(", rootpath=%s", root_server_path);

	if (ic_dev_mtu)

		printk(", mtu=%d", ic_dev_mtu);

	printk("\n");

#endif /* !SILENT */

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