ixgbe: Address fact that RSC was not setting GSO size for incoming frames

This patch is meant to address the fact that RSC has not been setting the
gso_size value on the skb.  As a result performance on lossy TCP
connections was negatively impacted.  This change resolves the issue by
setting gso_size to the average size for incoming packets.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 18e474c..762f337 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -1276,6 +1276,104 @@ static inline bool ixgbe_close_active_frag_list(struct sk_buff *head)
        return true;
 }
 
+/**
+ * ixgbe_get_headlen - determine size of header for RSC/LRO/GRO/FCOE
+ * @data: pointer to the start of the headers
+ * @max_len: total length of section to find headers in
+ *
+ * This function is meant to determine the length of headers that will
+ * be recognized by hardware for LRO, GRO, and RSC offloads.  The main
+ * motivation of doing this is to only perform one pull for IPv4 TCP
+ * packets so that we can do basic things like calculating the gso_size
+ * based on the average data per packet.
+ **/
+static unsigned int ixgbe_get_headlen(unsigned char *data,
+                                     unsigned int max_len)
+{
+       union {
+               unsigned char *network;
+               /* l2 headers */
+               struct ethhdr *eth;
+               struct vlan_hdr *vlan;
+               /* l3 headers */
+               struct iphdr *ipv4;
+       } hdr;
+       __be16 protocol;
+       u8 nexthdr = 0; /* default to not TCP */
+       u8 hlen;
+
+       /* this should never happen, but better safe than sorry */
+       if (max_len < ETH_HLEN)
+               return max_len;
+
+       /* initialize network frame pointer */
+       hdr.network = data;
+
+       /* set first protocol and move network header forward */
+       protocol = hdr.eth->h_proto;
+       hdr.network += ETH_HLEN;
+
+       /* handle any vlan tag if present */
+       if (protocol == __constant_htons(ETH_P_8021Q)) {
+               if ((hdr.network - data) > (max_len - VLAN_HLEN))
+                       return max_len;
+
+               protocol = hdr.vlan->h_vlan_encapsulated_proto;
+               hdr.network += VLAN_HLEN;
+       }
+
+       /* handle L3 protocols */
+       if (protocol == __constant_htons(ETH_P_IP)) {
+               if ((hdr.network - data) > (max_len - sizeof(struct iphdr)))
+                       return max_len;
+
+               /* access ihl as a u8 to avoid unaligned access on ia64 */
+               hlen = (hdr.network[0] & 0x0F) << 2;
+
+               /* verify hlen meets minimum size requirements */
+               if (hlen < sizeof(struct iphdr))
+                       return hdr.network - data;
+
+               /* record next protocol */
+               nexthdr = hdr.ipv4->protocol;
+               hdr.network += hlen;
+#ifdef CONFIG_FCOE
+       } else if (protocol == __constant_htons(ETH_P_FCOE)) {
+               if ((hdr.network - data) > (max_len - FCOE_HEADER_LEN))
+                       return max_len;
+               hdr.network += FCOE_HEADER_LEN;
+#endif
+       } else {
+               return hdr.network - data;
+       }
+
+       /* finally sort out TCP */
+       if (nexthdr == IPPROTO_TCP) {
+               if ((hdr.network - data) > (max_len - sizeof(struct tcphdr)))
+                       return max_len;
+
+               /* access doff as a u8 to avoid unaligned access on ia64 */
+               hlen = (hdr.network[12] & 0xF0) >> 2;
+
+               /* verify hlen meets minimum size requirements */
+               if (hlen < sizeof(struct tcphdr))
+                       return hdr.network - data;
+
+               hdr.network += hlen;
+       }
+
+       /*
+        * If everything has gone correctly hdr.network should be the
+        * data section of the packet and will be the end of the header.
+        * If not then it probably represents the end of the last recognized
+        * header.
+        */
+       if ((hdr.network - data) < max_len)
+               return hdr.network - data;
+       else
+               return max_len;
+}
+
 static void ixgbe_get_rsc_cnt(struct ixgbe_ring *rx_ring,
                              union ixgbe_adv_rx_desc *rx_desc,
                              struct sk_buff *skb)
@@ -1299,6 +1397,32 @@ static void ixgbe_get_rsc_cnt(struct ixgbe_ring *rx_ring,
        IXGBE_CB(skb)->append_cnt += rsc_cnt - 1;
 }
 
+static void ixgbe_set_rsc_gso_size(struct ixgbe_ring *ring,
+                                  struct sk_buff *skb)
+{
+       u16 hdr_len = ixgbe_get_headlen(skb->data, skb_headlen(skb));
+
+       /* set gso_size to avoid messing up TCP MSS */
+       skb_shinfo(skb)->gso_size = DIV_ROUND_UP((skb->len - hdr_len),
+                                                IXGBE_CB(skb)->append_cnt);
+}
+
+static void ixgbe_update_rsc_stats(struct ixgbe_ring *rx_ring,
+                                  struct sk_buff *skb)
+{
+       /* if append_cnt is 0 then frame is not RSC */
+       if (!IXGBE_CB(skb)->append_cnt)
+               return;
+
+       rx_ring->rx_stats.rsc_count += IXGBE_CB(skb)->append_cnt;
+       rx_ring->rx_stats.rsc_flush++;
+
+       ixgbe_set_rsc_gso_size(rx_ring, skb);
+
+       /* gso_size is computed using append_cnt so always clear it last */
+       IXGBE_CB(skb)->append_cnt = 0;
+}
+
 static bool ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
                               struct ixgbe_ring *rx_ring,
                               int budget)
@@ -1437,11 +1561,7 @@ static bool ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
                        goto next_desc;
                }
 
-               if (IXGBE_CB(skb)->append_cnt) {
-                       rx_ring->rx_stats.rsc_count +=
-                                       IXGBE_CB(skb)->append_cnt;
-                       rx_ring->rx_stats.rsc_flush++;
-               }
+               ixgbe_update_rsc_stats(rx_ring, skb);
 
                /* ERR_MASK will only have valid bits if EOP set */
                if (unlikely(staterr & IXGBE_RXDADV_ERR_FRAME_ERR_MASK)) {