IPoIB: improve IPv4/IPv6 to IB mcast mapping functions

An IPoIB subnet on an IB fabric that spans multiple IB subnets can't
use link-local scope in multicast GIDs.  The existing routines that
map IP/IPv6 multicast addresses into IB link-level addresses hard-code
the scope to link-local, and they also leave the partition key field
uninitialised.  This patch adds a parameter (the link-level broadcast
address) to the mapping routines, allowing them to initialise both the
scope and the P_Key appropriately, and fixes up the call sites.

The next step will be to add a way to configure the scope for an IPoIB
interface.

Signed-off-by: Rolf Manderscheid <rvm@obsidianresearch.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 448eccb20638..b24508abb850 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -269,18 +269,21 @@ static inline void ipv6_arcnet_mc_map(const struct in6_addr *addr, char *buf)
         buf[0] = 0x00;
 }
 
-static inline void ipv6_ib_mc_map(struct in6_addr *addr, char *buf)
+static inline void ipv6_ib_mc_map(const struct in6_addr *addr,
+                                  const unsigned char *broadcast, char *buf)
 {
+        unsigned char scope = broadcast[5] & 0xF;
+
         buf[0]  = 0;            /* Reserved */
         buf[1]  = 0xff;         /* Multicast QPN */
         buf[2]  = 0xff;
         buf[3]  = 0xff;
         buf[4]  = 0xff;
-        buf[5]  = 0x12;         /* link local scope */
+        buf[5]  = 0x10 | scope; /* scope from broadcast address */
         buf[6]  = 0x60;         /* IPv6 signature */
         buf[7]  = 0x1b;
-        buf[8]  = 0;            /* P_Key */
-        buf[9]  = 0;
+        buf[8]  = broadcast[8]; /* P_Key */
+        buf[9]  = broadcast[9];
         memcpy(buf + 10, addr->s6_addr + 6, 10);
 }
 #endif