ipv4: ipmr: support multiple tables

This patch adds support for multiple independant multicast routing instances,
named "tables".

Userspace multicast routing daemons can bind to a specific table instance by
issuing a setsockopt call using a new option MRT_TABLE. The table number is
stored in the raw socket data and affects all following ipmr setsockopt(),
getsockopt() and ioctl() calls. By default, a single table (RT_TABLE_DEFAULT)
is created with a default routing rule pointing to it. Newly created pimreg
devices have the table number appended ("pimregX"), with the exception of
devices created in the default table, which are named just "pimreg" for
compatibility reasons.

Packets are directed to a specific table instance using routing rules,
similar to how regular routing rules work. Currently iif, oif and mark
are supported as keys, source and destination addresses could be supported
additionally.

Example usage:

- bind pimd/xorp/... to a specific table:

uint32_t table = 123;
setsockopt(fd, IPPROTO_IP, MRT_TABLE, &table, sizeof(table));

- create routing rules directing packets to the new table:

# ip mrule add iif eth0 lookup 123
# ip mrule add oif eth0 lookup 123

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 0 deletions

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index c9a1c68767f..be597749c38 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -250,6 +250,20 @@ config IP_MROUTE
           <file:Documentation/networking/multicast.txt>. If you haven't heard
           about it, you don't need it.
 
+config IP_MROUTE_MULTIPLE_TABLES
+        bool "IP: multicast policy routing"
+        depends on IP_ADVANCED_ROUTER
+        select FIB_RULES
+        help
+          Normally, a multicast router runs a userspace daemon and decides
+          what to do with a multicast packet based on the source and
+          destination addresses. If you say Y here, the multicast router
+          will also be able to take interfaces and packet marks into
+          account and run multiple instances of userspace daemons
+          simultaneously, each one handling a single table.
+
+          If unsure, say N.
+
 config IP_PIMSM_V1
         bool "IP: PIM-SM version 1 support"
         depends on IP_MROUTE