To use a NFS-root for UDP jumbo frames the kernel on the client need to bring
up interface with MTU set to 9000 bytes - otherwise it cannot contact server
with jumbo frames enabled (nfs server not responding, still trying) and cannot
boot. Added a kernel parameter named 'ipmtu' which can be used to specify
initial MTU size when booting via nfsroot.
Signed-off-by: Mariusz Bialonczyk <[EMAIL PROTECTED]>
diff -Nru linux-2.6.21.1-orig/Documentation/kernel-parameters.txt
linux-2.6.21.1/Documentation/kernel-parameters.txt
--- linux-2.6.21.1-orig/Documentation/kernel-parameters.txt 2007-04-27
23:49:26.000000000 +0200
+++ linux-2.6.21.1/Documentation/kernel-parameters.txt 2007-07-01
18:47:11.000000000 +0200
@@ -720,6 +720,9 @@
ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
See comment before ip2_setup() in drivers/char/ip2.c.
+ ipmtu= [IP_PNP]
+ See Documentation/nfsroot.txt.
+
ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
See header of drivers/scsi/ips.c.
diff -Nru linux-2.6.21.1-orig/Documentation/nfsroot.txt
linux-2.6.21.1/Documentation/nfsroot.txt
--- linux-2.6.21.1-orig/Documentation/nfsroot.txt 2007-04-27
23:49:26.000000000 +0200
+++ linux-2.6.21.1/Documentation/nfsroot.txt 2007-07-01 19:02:40.000000000
+0200
@@ -153,6 +153,16 @@
Default: any
+ipmtu=<mtu_value>
+
+ This parameter tells the kernel to override default MTU size to specified
+ <mtu_value>. Useful in cases where NFS server have jumbo frames enabled and
+ client can't connect via UDP because of default MTU value (in ethernet
+ usually 1500 bytes). With this option before bringing interface up, kernel
+ will set the passed MTU size. In case of NFS-root booting server and client
+ can use UDP jumbo frames (NFS's rsize and wsize set to 8192 for instance).
+
+
3.) Boot Loader
diff -Nru linux-2.6.21.1-orig/net/ipv4/ipconfig.c
linux-2.6.21.1/net/ipv4/ipconfig.c
--- linux-2.6.21.1-orig/net/ipv4/ipconfig.c 2007-04-27 23:49:26.000000000
+0200
+++ linux-2.6.21.1/net/ipv4/ipconfig.c 2007-07-01 15:44:44.000000000 +0200
@@ -113,6 +113,8 @@
*/
int ic_set_manually __initdata = 0; /* IPconfig parameters set
manually */
+unsigned int ic_mtu __initdata = 0; /* IPconfig MTU parameter: 0 -
defaults, other - override */
+
static int ic_enable __initdata = 0; /* IP config enabled? */
/* Protocol choice */
@@ -209,6 +211,11 @@
able &= ic_proto_enabled;
if (ic_proto_enabled && !able)
continue;
+ if (ic_mtu > 0)
+ {
+ printk(KERN_ERR "IP-Config: Overriding %s MTU
to %d bytes\n", dev->name, ic_mtu);
+ dev->mtu = ic_mtu;
+ }
oflags = dev->flags;
if (dev_change_flags(dev, oflags | IFF_UP) < 0) {
printk(KERN_ERR "IP-Config: Failed to open
%s\n", dev->name);
@@ -1506,5 +1513,14 @@
return ip_auto_config_setup(addrs);
}
+static int __init mtu_config_setup(char *str)
+{
+ if (!str)
+ return 0;
+ ic_mtu = simple_strtoul(str, &str, 0);
+ return 1;
+}
+
__setup("ip=", ip_auto_config_setup);
+__setup("ipmtu=", mtu_config_setup);
__setup("nfsaddrs=", nfsaddrs_config_setup);
-
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