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

[Eric Dumazet <eric.dumazet@gmail.com>]

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>