tunneling: Simplify path MTU discovery logic.

[sliver-openvswitch.git] / datapath / tunnel.c

diff --git a/datapath/tunnel.c b/datapath/tunnel.c
index 08906e4..bd3a9e0 100644 (file)
--- a/datapath/tunnel.c
+++ b/datapath/tunnel.c
@@ -716,54 +716,57 @@ static bool check_mtu(struct sk_buff *skb,
                      const struct tnl_mutable_config *mutable,
                      const struct rtable *rt, __be16 *frag_offp)
 {
+       bool pmtud = mutable->flags & TNL_F_PMTUD;
+       __be16 frag_off = 0;
        int mtu;
-       __be16 frag_off;
 
-       frag_off = (mutable->flags & TNL_F_PMTUD) ? htons(IP_DF) : 0;
-       if (frag_off)
+       if (pmtud) {
+               frag_off = htons(IP_DF);
+
                mtu = dst_mtu(&rt_dst(rt))
                        - ETH_HLEN
                        - mutable->tunnel_hlen
-                       - (eth_hdr(skb)->h_proto == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);
-       else
-               mtu = mutable->mtu;
+                       - (eth_hdr(skb)->h_proto == htons(ETH_P_8021Q) ?
+                               VLAN_HLEN : 0);
+       }
 
        if (skb->protocol == htons(ETH_P_IP)) {
-               struct iphdr *old_iph = ip_hdr(skb);
+               struct iphdr *iph = ip_hdr(skb);
+
+               frag_off |= iph->frag_off & htons(IP_DF);
 
-               frag_off |= old_iph->frag_off & htons(IP_DF);
-               mtu = max(mtu, IP_MIN_MTU);
+               if (pmtud && iph->frag_off & htons(IP_DF)) {
+                       mtu = max(mtu, IP_MIN_MTU);
 
-               if ((old_iph->frag_off & htons(IP_DF)) &&
-                   mtu < ntohs(old_iph->tot_len)) {
-                       if (tnl_frag_needed(vport, mutable, skb, mtu, OVS_CB(skb)->tun_id))
-                               goto drop;
+                       if (ntohs(iph->tot_len) > mtu &&
+                           tnl_frag_needed(vport, mutable, skb, mtu,
+                                           OVS_CB(skb)->tun_id))
+                               return false;
                }
        }
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
        else if (skb->protocol == htons(ETH_P_IPV6)) {
                unsigned int packet_length = skb->len - ETH_HLEN
-                       - (eth_hdr(skb)->h_proto == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);
-
-               mtu = max(mtu, IPV6_MIN_MTU);
+                       - (eth_hdr(skb)->h_proto == htons(ETH_P_8021Q) ?
+                               VLAN_HLEN : 0);
 
                /* IPv6 requires PMTUD if the packet is above the minimum MTU. */
                if (packet_length > IPV6_MIN_MTU)
                        frag_off = htons(IP_DF);
 
-               if (mtu < packet_length) {
-                       if (tnl_frag_needed(vport, mutable, skb, mtu, OVS_CB(skb)->tun_id))
-                               goto drop;
+               if (pmtud) {
+                       mtu = max(mtu, IPV6_MIN_MTU);
+
+                       if (packet_length > mtu &&
+                           tnl_frag_needed(vport, mutable, skb, mtu,
+                                           OVS_CB(skb)->tun_id))
+                               return false;
                }
        }
 #endif
 
        *frag_offp = frag_off;
        return true;
-
-drop:
-       *frag_offp = 0;
-       return false;
 }
 
 static void create_tunnel_header(const struct vport *vport,
@@ -1151,7 +1154,7 @@ int tnl_send(struct vport *vport, struct sk_buff *skb)
        struct dst_entry *unattached_dst = NULL;
        struct tnl_cache *cache;
        int sent_len = 0;
-       __be16 frag_off;
+       __be16 frag_off = 0;
        u8 ttl;
        u8 inner_tos;
        u8 tos;