flow_dissector: factor out the ports extraction in skb_flow_get_ports

Factor out the code that extracts the ports from skb_flow_dissect and
add a new function skb_flow_get_ports which can be re-used.

Suggested-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 11 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 8d7d0dd72db2..f8e25ac41c6c 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -25,9 +25,35 @@ static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *i
         memcpy(&flow->src, &iph->saddr, sizeof(flow->src) + sizeof(flow->dst));
 }
 
+/**
+ * skb_flow_get_ports - extract the upper layer ports and return them
+ * @skb: buffer to extract the ports from
+ * @thoff: transport header offset
+ * @ip_proto: protocol for which to get port offset
+ *
+ * The function will try to retrieve the ports at offset thoff + poff where poff
+ * is the protocol port offset returned from proto_ports_offset
+ */
+__be32 skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto)
+{
+        int poff = proto_ports_offset(ip_proto);
+
+        if (poff >= 0) {
+                __be32 *ports, _ports;
+
+                ports = skb_header_pointer(skb, thoff + poff,
+                                           sizeof(_ports), &_ports);
+                if (ports)
+                        return *ports;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL(skb_flow_get_ports);
+
 bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
 {
-        int poff, nhoff = skb_network_offset(skb);
+        int nhoff = skb_network_offset(skb);
         u8 ip_proto;
         __be16 proto = skb->protocol;
 
@@ -150,16 +176,7 @@ ipv6:
         }
 
         flow->ip_proto = ip_proto;
-        poff = proto_ports_offset(ip_proto);
-        if (poff >= 0) {
-                __be32 *ports, _ports;
-
-                ports = skb_header_pointer(skb, nhoff + poff,
-                                           sizeof(_ports), &_ports);
-                if (ports)
-                        flow->ports = *ports;
-        }
-
+        flow->ports = skb_flow_get_ports(skb, nhoff, ip_proto);
         flow->thoff = (u16) nhoff;
 
         return true;