[ipoib] Clarify new role of IPoIB peer cache as for MAC addresses only

Now that path record lookups are handled entirely via
ib_resolve_path(), the only role of the IPoIB peer cache is as a
lookup table for MAC addresses.  Update the code structure and
comments to reflect this.

diff --git a/src/drivers/net/ipoib.c b/src/drivers/net/ipoib.c
index e94b200..bf77887 100644 (file)
--- a/src/drivers/net/ipoib.c
+++ b/src/drivers/net/ipoib.c
@@ -100,8 +100,12 @@ static struct ipoib_mac ipoib_broadcast = {
 /**
  * IPoIB peer address
  *
- * This serves a similar role to the ARP cache for Ethernet.  (ARP
- * *is* used on IPoIB; we have two caches to maintain.)
+ * The IPoIB link-layer header is only four bytes long and so does not
+ * have sufficient room to store IPoIB MAC address(es).  We therefore
+ * maintain a cache of MAC addresses identified by a single-byte key,
+ * and abuse the spare two bytes within the link-layer header to
+ * communicate these MAC addresses between the link-layer code and the
+ * netdevice driver.
  */
 struct ipoib_peer {
        /** Key */
@@ -145,28 +149,6 @@ static struct ipoib_peer * ipoib_lookup_peer_by_key ( unsigned int key ) {
        return NULL;
 }
 
-/**
- * Look up cached peer by GID
- *
- * @v gid              Peer GID
- * @ret peer           Peer cache entry, or NULL
- */
-static struct ipoib_peer *
-ipoib_lookup_peer_by_gid ( const struct ib_gid *gid ) {
-       struct ipoib_peer *peer;
-       unsigned int i;
-
-       for ( i = 0 ; i < IPOIB_NUM_CACHED_PEERS ; i++ ) {
-               peer = &ipoib_peer_cache[i];
-               if ( memcmp ( &peer->mac.gid, gid,
-                             sizeof ( peer->mac.gid) ) == 0 ) {
-                       return peer;
-               }
-       }
-
-       return NULL;
-}
-
 /**
  * Store GID and QPN in peer cache
  *
@@ -174,16 +156,16 @@ ipoib_lookup_peer_by_gid ( const struct ib_gid *gid ) {
  * @v qpn              Peer QPN
  * @ret peer           Peer cache entry
  */
-static struct ipoib_peer *
-ipoib_cache_peer ( const struct ib_gid *gid, unsigned long qpn ) {
+static struct ipoib_peer * ipoib_cache_peer ( const struct ipoib_mac *mac ) {
        struct ipoib_peer *peer;
        unsigned int key;
+       unsigned int i;
 
        /* Look for existing cache entry */
-       peer = ipoib_lookup_peer_by_gid ( gid );
-       if ( peer ) {
-               assert ( peer->mac.qpn = ntohl ( qpn ) );
-               return peer;
+       for ( i = 0 ; i < IPOIB_NUM_CACHED_PEERS ; i++ ) {
+               peer = &ipoib_peer_cache[i];
+               if ( memcmp ( &peer->mac, mac, sizeof ( peer->mac ) ) == 0 )
+                       return peer;
        }
 
        /* No entry found: create a new one */
@@ -194,12 +176,9 @@ ipoib_cache_peer ( const struct ib_gid *gid, unsigned long qpn ) {
 
        memset ( peer, 0, sizeof ( *peer ) );
        peer->key = key;
-       peer->mac.qpn = htonl ( qpn );
-       memcpy ( &peer->mac.gid, gid, sizeof ( peer->mac.gid ) );
-       DBG ( "IPoIB peer %x has GID %08x:%08x:%08x:%08x and QPN %lx\n",
-             peer->key, htonl ( gid->u.dwords[0] ),
-             htonl ( gid->u.dwords[1] ), htonl ( gid->u.dwords[2] ),
-             htonl ( gid->u.dwords[3] ), qpn );
+       memcpy ( &peer->mac, mac, sizeof ( peer->mac ) );
+       DBG ( "IPoIB peer %x has MAC %s\n",
+             peer->key, ipoib_ntoa ( &peer->mac ) );
        return peer;
 }
 
@@ -231,8 +210,8 @@ static int ipoib_push ( struct net_device *netdev __unused,
        struct ipoib_peer *src;
 
        /* Add link-layer addresses to cache */
-       dest = ipoib_cache_peer ( &dest_mac->gid, ntohl ( dest_mac->qpn ) );
-       src = ipoib_cache_peer ( &src_mac->gid, ntohl ( src_mac->qpn ) );
+       dest = ipoib_cache_peer ( dest_mac );
+       src = ipoib_cache_peer ( src_mac );
 
        /* Build IPoIB header */
        ipoib_hdr->proto = net_proto;
@@ -497,6 +476,7 @@ static void ipoib_data_complete_recv ( struct ib_device *ibdev __unused,
        struct ipoib_device *ipoib = ib_qp_get_ownerdata ( qp );
        struct net_device *netdev = ipoib->netdev;
        struct ipoib_hdr *ipoib_hdr;
+       struct ipoib_mac ll_src;
        struct ipoib_peer *src;
 
        if ( rc != 0 ) {
@@ -516,7 +496,9 @@ static void ipoib_data_complete_recv ( struct ib_device *ibdev __unused,
 
        /* Parse source address */
        if ( av->gid_present ) {
-               src = ipoib_cache_peer ( &av->gid, av->qpn );
+               ll_src.qpn = htonl ( av->qpn );
+               memcpy ( &ll_src.gid, &av->gid, sizeof ( ll_src.gid ) );
+               src = ipoib_cache_peer ( &ll_src );
                ipoib_hdr->u.peer.src = src->key;
        }