datapath: Use multicast groups allocated for upcalls.

We allocate a number of multicast groups and stripe upcalls across
them using a hash function.  However, instead of using the ID of
the selected group for the upcall multicast we were directly using
the output of the hash function.  In the best case this leads to
intermittent failures when we choose an invalid group ID (such as
0) or in the worse case could lead to access of unallocated memory.
This fixes that by looking up the group we have been allocated.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 10eb5b7..544f8cd 100644 (file)
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -79,6 +79,8 @@ EXPORT_SYMBOL(dp_ioctl_hook);
 static LIST_HEAD(dps);
 
 static struct vport *new_vport(const struct vport_parms *);
+static int queue_control_packets(struct datapath *, struct sk_buff *,
+                                const struct dp_upcall_info *);
 
 /* Must be called with rcu_read_lock, genl_mutex, or RTNL lock. */
 struct datapath *get_dp(int dp_ifindex)
@@ -365,13 +367,94 @@ static void copy_and_csum_skb(struct sk_buff *skb, void *to)
        *(__sum16 *)(to + csum_start + csum_offset) = csum_fold(csum);
 }
 
-static struct genl_family dp_packet_genl_family;
+static struct genl_family dp_packet_genl_family = {
+       .id = GENL_ID_GENERATE,
+       .hdrsize = sizeof(struct odp_header),
+       .name = ODP_PACKET_FAMILY,
+       .version = 1,
+       .maxattr = ODP_PACKET_ATTR_MAX
+};
+
+/* Generic Netlink multicast groups for upcalls.
+ *
+ * We really want three unique multicast groups per datapath, but we can't even
+ * get one, because genl_register_mc_group() takes genl_lock, which is also
+ * held during Generic Netlink message processing, so trying to acquire
+ * multicast groups during ODP_DP_NEW processing deadlocks.  Instead, we
+ * preallocate a few groups and use them round-robin for datapaths.  Collision
+ * isn't fatal--multicast listeners should check that the family is the one
+ * that they want and discard others--but it wastes time and memory to receive
+ * unwanted messages.
+ */
 #define PACKET_N_MC_GROUPS 16
+static struct genl_multicast_group packet_mc_groups[PACKET_N_MC_GROUPS];
 
-static int packet_mc_group(struct datapath *dp, u8 cmd)
+static u32 packet_mc_group(struct datapath *dp, u8 cmd)
 {
+       u32 idx;
        BUILD_BUG_ON_NOT_POWER_OF_2(PACKET_N_MC_GROUPS);
-       return jhash_2words(dp->dp_ifindex, cmd, 0) & (PACKET_N_MC_GROUPS - 1);
+
+       idx = jhash_2words(dp->dp_ifindex, cmd, 0) & (PACKET_N_MC_GROUPS - 1);
+       return packet_mc_groups[idx].id;
+}
+
+static int packet_register_mc_groups(void)
+{
+       int i;
+
+       for (i = 0; i < PACKET_N_MC_GROUPS; i++) {
+               struct genl_multicast_group *group = &packet_mc_groups[i];
+               int error;
+
+               sprintf(group->name, "packet%d", i);
+               error = genl_register_mc_group(&dp_packet_genl_family, group);
+               if (error)
+                       return error;
+       }
+       return 0;
+}
+
+int dp_upcall(struct datapath *dp, struct sk_buff *skb, const struct dp_upcall_info *upcall_info)
+{
+       struct dp_stats_percpu *stats;
+       int err;
+
+       WARN_ON_ONCE(skb_shared(skb));
+
+       forward_ip_summed(skb);
+
+       err = vswitch_skb_checksum_setup(skb);
+       if (err)
+               goto err_kfree_skb;
+
+       /* Break apart GSO packets into their component pieces.  Otherwise
+        * userspace may try to stuff a 64kB packet into a 1500-byte MTU. */
+       if (skb_is_gso(skb)) {
+               struct sk_buff *nskb = skb_gso_segment(skb, NETIF_F_SG | NETIF_F_HW_CSUM);
+               
+               kfree_skb(skb);
+               skb = nskb;
+               if (IS_ERR(skb)) {
+                       err = PTR_ERR(skb);
+                       goto err;
+               }
+       }
+
+       return queue_control_packets(dp, skb, upcall_info);
+
+err_kfree_skb:
+       kfree_skb(skb);
+err:
+       local_bh_disable();
+       stats = per_cpu_ptr(dp->stats_percpu, smp_processor_id());
+
+       write_seqcount_begin(&stats->seqlock);
+       stats->n_lost++;
+       write_seqcount_end(&stats->seqlock);
+
+       local_bh_enable();
+
+       return err;
 }
 
 /* Send each packet in the 'skb' list to userspace for 'dp' as directed by
@@ -461,86 +544,6 @@ err_kfree_skbs:
        return err;
 }
 
-/* Generic Netlink multicast groups for upcalls.
- *
- * We really want three unique multicast groups per datapath, but we can't even
- * get one, because genl_register_mc_group() takes genl_lock, which is also
- * held during Generic Netlink message processing, so trying to acquire
- * multicast groups during ODP_DP_NEW processing deadlocks.  Instead, we
- * preallocate a few groups and use them round-robin for datapaths.  Collision
- * isn't fatal--multicast listeners should check that the family is the one
- * that they want and discard others--but it wastes time and memory to receive
- * unwanted messages.
- */
-static struct genl_multicast_group packet_mc_groups[PACKET_N_MC_GROUPS];
-
-static struct genl_family dp_packet_genl_family = {
-       .id = GENL_ID_GENERATE,
-       .hdrsize = sizeof(struct odp_header),
-       .name = ODP_PACKET_FAMILY,
-       .version = 1,
-       .maxattr = ODP_PACKET_ATTR_MAX
-};
-
-static int packet_register_mc_groups(void)
-{
-       int i;
-
-       for (i = 0; i < PACKET_N_MC_GROUPS; i++) {
-               struct genl_multicast_group *group = &packet_mc_groups[i];
-               int error;
-
-               sprintf(group->name, "packet%d", i);
-               error = genl_register_mc_group(&dp_packet_genl_family, group);
-               if (error)
-                       return error;
-       }
-       return 0;
-}
-
-int dp_upcall(struct datapath *dp, struct sk_buff *skb, const struct dp_upcall_info *upcall_info)
-{
-       struct dp_stats_percpu *stats;
-       int err;
-
-       WARN_ON_ONCE(skb_shared(skb));
-
-       forward_ip_summed(skb);
-
-       err = vswitch_skb_checksum_setup(skb);
-       if (err)
-               goto err_kfree_skb;
-
-       /* Break apart GSO packets into their component pieces.  Otherwise
-        * userspace may try to stuff a 64kB packet into a 1500-byte MTU. */
-       if (skb_is_gso(skb)) {
-               struct sk_buff *nskb = skb_gso_segment(skb, NETIF_F_SG | NETIF_F_HW_CSUM);
-               
-               kfree_skb(skb);
-               skb = nskb;
-               if (IS_ERR(skb)) {
-                       err = PTR_ERR(skb);
-                       goto err;
-               }
-       }
-
-       return queue_control_packets(dp, skb, upcall_info);
-
-err_kfree_skb:
-       kfree_skb(skb);
-err:
-       local_bh_disable();
-       stats = per_cpu_ptr(dp->stats_percpu, smp_processor_id());
-
-       write_seqcount_begin(&stats->seqlock);
-       stats->n_lost++;
-       write_seqcount_end(&stats->seqlock);
-
-       local_bh_enable();
-
-       return err;
-}
-
 /* Called with genl_mutex. */
 static int flush_flows(int dp_ifindex)
 {