RDMA/core: Use route entry flag to decide on loopback traffic

addr_resolve() considers a destination to be local if the next-hop
device of the resolved route for the destination is the loopback
netdevice.

This fails when the source and destination IP addresses belong to
a netdev enslaved to a VRF netdev. In this case the next-hop device
is the VRF itself:

 $ ip link add name myvrf up type vrf table 100
 $ ip link set ens2f0np0 master myvrf up
 $ ip addr add 192.168.1.1/24 dev ens2f0np0
 $ ip route get 192.168.1.1 oif myvrf
 local 192.168.1.1 dev myvrf table 100 src 192.168.1.1 uid 0
    cache <local>

This results in packets being generated with an incorrect destination
MAC of the VRF netdevice and ib_write_bw failing with timeout.

Solve this by determining if a destination is local or not based on
the resolved route's type rather than based on its next-hop netdevice
loopback flag.

This enables to resolve loopback traffic with and without VRF
configurations in a uniform way.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Vlad Dumitrescu <vdumitrescu@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20250916111103.84069-4-edwards@nvidia.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
index ca86c482662fb874d237bc8e4f162cb2e1711cfe..61596cda2b65f355ab945f9ad41638de7b0dceb7 100644 (file)
--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -446,31 +446,40 @@ static int addr6_resolve(struct sockaddr *src_sock,
 }
 #endif
 
+static bool is_dst_local(const struct dst_entry *dst)
+{
+       if (dst->ops->family == AF_INET)
+               return !!(dst_rtable(dst)->rt_type & RTN_LOCAL);
+       else if (dst->ops->family == AF_INET6)
+               return !!(dst_rt6_info(dst)->rt6i_flags & RTF_LOCAL);
+       else
+               return false;
+}
+
 static int addr_resolve_neigh(const struct dst_entry *dst,
                              const struct sockaddr *dst_in,
                              struct rdma_dev_addr *addr,
-                             unsigned int ndev_flags,
                              u32 seq)
 {
-       int ret = 0;
-
-       if (ndev_flags & IFF_LOOPBACK)
+       if (is_dst_local(dst)) {
+               /* When the destination is local entry, source and destination
+                * are same. Skip the neighbour lookup.
+                */
                memcpy(addr->dst_dev_addr, addr->src_dev_addr, MAX_ADDR_LEN);
-       else
-               ret = fetch_ha(dst, addr, dst_in, seq);
-       return ret;
+               return 0;
+       }
+
+       return fetch_ha(dst, addr, dst_in, seq);
 }
 
 static int rdma_set_src_addr_rcu(struct rdma_dev_addr *dev_addr,
-                                unsigned int *ndev_flags,
                                 const struct sockaddr *dst_in,
                                 const struct dst_entry *dst)
 {
        struct net_device *ndev = READ_ONCE(dst->dev);
 
-       *ndev_flags = ndev->flags;
        /* A physical device must be the RDMA device to use */
-       if (ndev->flags & IFF_LOOPBACK) {
+       if (is_dst_local(dst)) {
                int ret;
                /*
                 * RDMA (IB/RoCE, iWarp) doesn't run on lo interface or
@@ -538,7 +547,6 @@ static int addr_resolve(struct sockaddr *src_in,
                        u32 seq)
 {
        struct dst_entry *dst = NULL;
-       unsigned int ndev_flags = 0;
        struct rtable *rt = NULL;
        int ret;
 
@@ -575,7 +583,7 @@ static int addr_resolve(struct sockaddr *src_in,
                rcu_read_unlock();
                goto done;
        }
-       ret = rdma_set_src_addr_rcu(addr, &ndev_flags, dst_in, dst);
+       ret = rdma_set_src_addr_rcu(addr, dst_in, dst);
        rcu_read_unlock();
 
        /*
@@ -583,7 +591,7 @@ static int addr_resolve(struct sockaddr *src_in,
         * only if src addr translation didn't fail.
         */
        if (!ret && resolve_neigh)
-               ret = addr_resolve_neigh(dst, dst_in, addr, ndev_flags, seq);
+               ret = addr_resolve_neigh(dst, dst_in, addr, seq);
 
        if (src_in->sa_family == AF_INET)
                ip_rt_put(rt);