• Hannes Frederic Sowa's avatar
    ipv4: yet another new IP_MTU_DISCOVER option IP_PMTUDISC_OMIT · 1b346576
    Hannes Frederic Sowa authored
    IP_PMTUDISC_INTERFACE has a design error: because it does not allow the
    generation of fragments if the interface mtu is exceeded, it is very
    hard to make use of this option in already deployed name server software
    for which I introduced this option.
    
    This patch adds yet another new IP_MTU_DISCOVER option to not honor any
    path mtu information and not accepting new icmp notifications destined for
    the socket this option is enabled on. But we allow outgoing fragmentation
    in case the packet size exceeds the outgoing interface mtu.
    
    As such this new option can be used as a drop-in replacement for
    IP_PMTUDISC_DONT, which is currently in use by most name server software
    making the adoption of this option very smooth and easy.
    
    The original advantage of IP_PMTUDISC_INTERFACE is still maintained:
    ignoring incoming path MTU updates and not honoring discovered path MTUs
    in the output path.
    
    Fixes: 482fc609 ("ipv4: introduce new IP_MTU_DISCOVER mode IP_PMTUDISC_INTERFACE")
    Cc: Florian Weimer <fweimer@redhat.com>
    Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    1b346576
ip_output.c 38 KB