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Re: linux-ipsec: cornered: MTU and fragmentation bugs

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> The place John Denker speaks of is in ip_fragment.  If a packet is
> sent to ip_fragment() (such as at the end of ip_output()) without
> checking DF, then the packet gets dropped silently.


> > No patch ever seen.
> 
> In case you didn't get it:

This doesnt appear to make sense.

> - --- 685,693 ----
>         if (iph->frag_off & htons(IP_DF))
>         {
>                 ip_statistics.IpFragFails++;
>                 NETDEBUG(printk("ip_queue_xmit: frag needed\n"));
> +
> icmp_send(skb,ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED,htons(dev->mtu)
> , dev); /* jsd */
>                 return;

This shouldnt be causing any problems because for all the cases that matter
its handled higher up

Viz:
	IGMP - never sets DF
	ip_forward - checks DF
	UDP - references it in 2.0 but doesnt use it
	TCP - uses DF and sets the MTU below the point it will fragment
		locally.
	
The only case I can see where it might be relevant and a bug is looping back
an oversized multicast frame when running as a multicast router.

Can someone tell me under what circumstances they observed the event
occuring >

Alan
References: