From 9643f4551255ce8b3ef7470aaaf7f435a20f9182 Mon Sep 17 00:00:00 2001 From: Chris Friesen Date: Tue, 19 May 2009 15:31:50 -0700 Subject: 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 Signed-off-by: David S. Miller --- net/ipv4/ipconfig.c | 41 +++++++++++++++++++++++++++++++++++++---- 1 file changed, 37 insertions(+), 4 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c index 88bf051d0cbb..f8d04c256454 100644 --- a/net/ipv4/ipconfig.c +++ b/net/ipv4/ipconfig.c @@ -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 */ -- cgit v1.2.3