udp: only do GSO if # of segs > 1

[ Upstream commit 4094871db1d65810acab3d57f6089aa39ef7f648 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 3dda209f9e7928d281888466f43131e50a15b545..5e5d0575a43cc1cfd6ad0238cd0f4161b24090f8 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 a23580d2af8cf30dfb1889d4169c00f372154804..0454a8a3b39c3c216bdfaa43453505189d6ed9d9 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,
        },
        {