Re: [PATCH v7 1/2] ipv4: Implement IP_UNICAST_IF socket option.

[David Miller <davem@davemloft.net>]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 08 Feb 2012 20:28:43 +0100

> Le mercredi 08 février 2012 à 12:11 -0700, Erich E. Hoover a écrit :
>> The IP_UNICAST_IF feature is needed by the Wine project.  This patch
>> implements the feature by setting the outgoing interface in a similar
>> fashion to that of IP_MULTICAST_IF.  A separate option is needed to
>> handle this feature since the existing options do not provide all of
>> the characteristics required by IP_UNICAST_IF, a summary is provided
>> below.
>> 
>> SO_BINDTODEVICE:
>> * SO_BINDTODEVICE requires administrative privileges, IP_UNICAST_IF
>> does not.  From reading some old mailing list articles my
>> understanding is that SO_BINDTODEVICE requires administrative
>> privileges because it can override the administrator's routing
>> settings.
>> * The SO_BINDTODEVICE option restricts both outbound and inbound
>> traffic, IP_UNICAST_IF only impacts outbound traffic.
>> 
>> IP_PKTINFO:
>> * Since IP_PKTINFO and IP_UNICAST_IF are independent options,
>> implementing IP_UNICAST_IF with IP_PKTINFO will likely break some
>> applications.
>> * Implementing IP_UNICAST_IF on top of IP_PKTINFO significantly
>> complicates the Wine codebase and reduces the socket performance
>> (doing this requires a lot of extra communication between the
>> "server" and "user" layers).
>> 
>> bind():
>> * bind() does not work on broadcast packets, IP_UNICAST_IF is
>> specifically intended to work with broadcast packets.
>> * Like SO_BINDTODEVICE, bind() restricts both outbound and inbound
>> traffic.
>> 
>> Signed-off-by: Erich E. Hoover <ehoover@mines.edu>
>> ---
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

Applied.