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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: Chris Friesen <cfriesen@nortel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Chris Friesen 2009-05-19 15:31:50 -07:00 committed by David S. Miller
parent fd2120ca0d
commit 9643f45512
1 changed files with 37 additions and 4 deletions
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41
net/ipv4/ipconfig.c
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@ -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 */