netdev - ping6 sets IPV6_PMTUDISC_DO option on multicast packets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <473E0BA5.9070804@mvista.com>
Date:	Fri, 16 Nov 2007 14:29:09 -0700
From:	Tushar Gohad <tgohad@...sta.com>
To:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
Cc:	netdev@...r.kernel.org
Subject: ping6 sets IPV6_PMTUDISC_DO option on multicast packets


Yoshifuji-san,

I noticed that ping6 forces the IPV6_PMTUDISC_DO option on packets sent 
to multicast destinations. Is this a requirement?

Due to the following check recently introduced in the ip6_fragment() 
code, multicast packets that are over PMTU in size are never sent out, 
since ping6 code always sets the PMTUDISC_DO option and ip6_fragment() 
always fails.


=== net/ipv6/ip6_output.c ===

  573 static int ip6_fragment(struct sk_buff *skb, int (*output)
                              (struct sk_buff *))
  574 {
  ......
  592         /* We must not fragment if the socket is set to force MTU
                 discovery
  ......

  596         if (!np || np->pmtudisc >= IPV6_PMTUDISC_DO) {
  597                 skb->dev = skb->dst->dev;
  598                 icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu,
                                    skb->dev);
  599                 IP6_INC_STATS(ip6_dst_idev(skb->dst),
                                    IPSTATS_MIB_FRAGFAILS);
  600                 kfree_skb(skb);
  601                 return -EMSGSIZE;
  602         }
  ......
--


This check in the kernel code makes perfect sense, since the option is 
implies "do not fragment."

Should the ping6 code be fixed in that case?


Thanks,
- Tushar
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html