From 76e21053b5bf33a07c76f99d27a74238310e3c71 Mon Sep 17 00:00:00 2001 From: "Erich E. Hoover" Date: Wed, 8 Feb 2012 09:11:07 +0000 Subject: ipv4: Implement IP_UNICAST_IF socket option. 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 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/in.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/in.h') diff --git a/include/linux/in.h b/include/linux/in.h index 01129c0ea87c..e0337f11d92e 100644 --- a/include/linux/in.h +++ b/include/linux/in.h @@ -111,6 +111,7 @@ struct in_addr { #define MCAST_LEAVE_SOURCE_GROUP 47 #define MCAST_MSFILTER 48 #define IP_MULTICAST_ALL 49 +#define IP_UNICAST_IF 50 #define MCAST_EXCLUDE 0 #define MCAST_INCLUDE 1 -- cgit v1.2.3-59-g8ed1b