flow_dissector: add meaningful comments

Documents two piece of code which can't be understood at a glance.

Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index 90bd210..7747af3 100644 (file)
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -282,6 +282,7 @@ struct flow_keys {
        struct flow_dissector_key_vlan cvlan;
        struct flow_dissector_key_keyid keyid;
        struct flow_dissector_key_ports ports;
+       /* 'addrs' must be the last member */
        struct flow_dissector_key_addrs addrs;
 };
 

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index dbf502c..bc22b38 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1408,6 +1408,9 @@ static inline size_t flow_keys_hash_length(const struct flow_keys *flow)
 {
        size_t diff = FLOW_KEYS_HASH_OFFSET + sizeof(flow->addrs);
        BUILD_BUG_ON((sizeof(*flow) - FLOW_KEYS_HASH_OFFSET) % sizeof(u32));
+       /* flow.addrs MUST be the last member in struct flow_keys because
+        * different L3 protocols have different address length
+        */
        BUILD_BUG_ON(offsetof(typeof(*flow), addrs) !=
                     sizeof(*flow) - sizeof(flow->addrs));
 
@@ -1455,6 +1458,9 @@ __be32 flow_get_u32_dst(const struct flow_keys *flow)
 }
 EXPORT_SYMBOL(flow_get_u32_dst);
 
+/* Sort the source and destination IP (and the ports if the IP are the same),
+ * to have consistent hash within the two directions
+ */
 static inline void __flow_hash_consistentify(struct flow_keys *keys)
 {
        int addr_diff, i;