Messages in this thread | | | From | Denis Vlasenko <> | Subject | Re: [PATCH] Configure MTU via kernel DHCP | Date | Fri, 4 Feb 2005 10:06:49 +0200 |
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On Thursday 03 February 2005 06:47, Shane Hathaway wrote: > The attached patch enhances the kernel's DHCP client support (in > net/ipv4/ipconfig.c) to set the interface MTU if provided by the DHCP server. > Without this patch, it's difficult to netboot on a network that uses jumbo > frames. The patch is based on 2.6.10, but I'll update it to the latest > testing kernel if that would expedite its inclusion in the kernel. > > More background: it's currently difficult to netboot on a jumbo frame network > because when clients try to mount the root partition, they are still > configured with a small MTU and therefore reject packets sent by the > jumbo-frame-enabled NFS server. Linux needs to set the client MTU before > mounting any NFS shares. Fortunately, the DHCP protocol already supports > setting the MTU; this patch just integrates that feature into the kernel. > > Incidentally, ipconfig.c doesn't appear to do enough bounds checking on byte 1 > of DHCP/BOOTP extension fields (the length field). It looks like a malicious > DHCP server could mess with kernel memory that way. I could try to fix the > hole, but maybe someone more experienced with this code would like to verify > there's a problem first.
Long term solution is to use approptiately configured initramfs or initrd image and do above mentioned stuff in userspace. -- vda
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