udp: only do GSO if # of segs > 1

Prior to this change an application sending <= 1MSS worth of data and
enabling UDP GSO would fail if the system had SW GSO enabled, but the
same send would succeed if HW GSO offload is enabled. In addition to this
inconsistency the error in the SW GSO case does not get back to the
application if sending out of a real device so the user is unaware of this
failure.

With this change we only perform GSO if the # of segments is > 1 even
if the application has enabled segmentation. I've also updated the
relevant udpgso selftests.

Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT")
Signed-off-by: Josh Hunt <johunt@akamai.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 3e2b9018187995cc5afe67db3836264037b4d9f1..14bc654b6842003b325efe268041749c6770947f 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -821,6 +821,7 @@ static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
        int is_udplite = IS_UDPLITE(sk);
        int offset = skb_transport_offset(skb);
        int len = skb->len - offset;
+       int datalen = len - sizeof(*uh);
        __wsum csum = 0;
 
        /*
@@ -854,10 +855,12 @@ static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
                        return -EIO;
                }
 
-               skb_shinfo(skb)->gso_size = cork->gso_size;
-               skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
-               skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(len - sizeof(*uh),
-                                                        cork->gso_size);
+               if (datalen > cork->gso_size) {
+                       skb_shinfo(skb)->gso_size = cork->gso_size;
+                       skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
+                       skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(datalen,
+                                                                cork->gso_size);
+               }
                goto csum_partial;
        }
 

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index eb9a9934ac05d12dcc8ba8ea92e1e4429865d4ff..6324d3a8cb53dd76ea0deaf4358e33e529ce56ec 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1109,6 +1109,7 @@ static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
        __wsum csum = 0;
        int offset = skb_transport_offset(skb);
        int len = skb->len - offset;
+       int datalen = len - sizeof(*uh);
 
        /*
         * Create a UDP header
@@ -1141,10 +1142,12 @@ static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
                        return -EIO;
                }
 
-               skb_shinfo(skb)->gso_size = cork->gso_size;
-               skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
-               skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(len - sizeof(*uh),
-                                                        cork->gso_size);
+               if (datalen > cork->gso_size) {
+                       skb_shinfo(skb)->gso_size = cork->gso_size;
+                       skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
+                       skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(datalen,
+                                                                cork->gso_size);
+               }
                goto csum_partial;
        }
 

diff --git a/tools/testing/selftests/net/udpgso.c b/tools/testing/selftests/net/udpgso.c
index b8265ee9923f2b11af7884d365b2e5af9323ff3a..614b31aad168b35564e91d9cfaa364e06e73762c 100644 (file)
--- a/tools/testing/selftests/net/udpgso.c
+++ b/tools/testing/selftests/net/udpgso.c
@@ -89,12 +89,9 @@ struct testcase testcases_v4[] = {
                .tfail = true,
        },
        {
-               /* send a single MSS: will fail with GSO, because the segment
-                * logic in udp4_ufo_fragment demands a gso skb to be > MTU
-                */
+               /* send a single MSS: will fall back to no GSO */
                .tlen = CONST_MSS_V4,
                .gso_len = CONST_MSS_V4,
-               .tfail = true,
                .r_num_mss = 1,
        },
        {
@@ -139,10 +136,9 @@ struct testcase testcases_v4[] = {
                .tfail = true,
        },
        {
-               /* send a single 1B MSS: will fail, see single MSS above */
+               /* send a single 1B MSS: will fall back to no GSO */
                .tlen = 1,
                .gso_len = 1,
-               .tfail = true,
                .r_num_mss = 1,
        },
        {
@@ -196,12 +192,9 @@ struct testcase testcases_v6[] = {
                .tfail = true,
        },
        {
-               /* send a single MSS: will fail with GSO, because the segment
-                * logic in udp4_ufo_fragment demands a gso skb to be > MTU
-                */
+               /* send a single MSS: will fall back to no GSO */
                .tlen = CONST_MSS_V6,
                .gso_len = CONST_MSS_V6,
-               .tfail = true,
                .r_num_mss = 1,
        },
        {
@@ -246,10 +239,9 @@ struct testcase testcases_v6[] = {
                .tfail = true,
        },
        {
-               /* send a single 1B MSS: will fail, see single MSS above */
+               /* send a single 1B MSS: will fall back to no GSO */
                .tlen = 1,
                .gso_len = 1,
-               .tfail = true,
                .r_num_mss = 1,
        },
        {