netdev - Re: [PATCH v3 net-next] net: ipv6: Add sysctl entry to disable MTU updates from RA

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 for Android: free password hash cracker in your pocket

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

Message-ID: <8761btxxjm.fsf@nemi.mork.no>
Date:	Mon, 26 Jan 2015 18:27:09 +0100
From:	Bjørn Mork <bjorn@...k.no>
To:	David Miller <davem@...emloft.net>
Cc:	harouth@...eaurora.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 net-next] net: ipv6: Add sysctl entry to disable MTU updates from RA

David Miller <davem@...emloft.net> writes:

> Under what circumstances would userland ignore a router advertized
> MTU, and are the RFCs ok with this?

RFC 4861 ( https://tools.ietf.org/html/rfc4861#page-54 ) says:

  "If the MTU option is present, hosts SHOULD copy the option's value
   into LinkMTU so long as the value is greater than or equal to the
   minimum link MTU [IPv6] and does not exceed the maximum LinkMTU value
   specified in the link-type-specific document (e.g., [IPv6-ETHER])."

So the RFC acknowledge that there may exist valid reasons in particular
circumstances to ignore the MTU option.  As others have stated: This
might be necessary for DoS prevention, working around bugs in other
equipment, etc.


Bjørn
--
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