selftests: Calculate udpgso segment count without header adjustment

The below referenced commit correctly updated the computation of number
of segments (gso_size) by using only the gso payload size and
removing the header lengths.

With this change the regression test started failing. Update
the tests to match this new behavior.

Both IPv4 and IPv6 tests are updated, as a separate patch in this series
will update udp_v6_send_skb to match this change in udp_send_skb.

Fixes: 158390e4 ("udp: using datalen to cap max gso segments")
Signed-off-by: Coco Li <lixiaoyan@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20211223222441.2975883-2-lixiaoyan@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/udpgso.c

@@ -156,13 +156,13 @@ struct testcase testcases_v4[] = {
 	},
 	{
 		/* send max number of min sized segments */
-		.tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V4,
+		.tlen = UDP_MAX_SEGMENTS,
 		.gso_len = 1,
-		.r_num_mss = UDP_MAX_SEGMENTS - CONST_HDRLEN_V4,
+		.r_num_mss = UDP_MAX_SEGMENTS,
 	},
 	{
 		/* send max number + 1 of min sized segments: fail */
-		.tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V4 + 1,
+		.tlen = UDP_MAX_SEGMENTS + 1,
 		.gso_len = 1,
 		.tfail = true,
 	},
@@ -259,13 +259,13 @@ struct testcase testcases_v6[] = {
 	},
 	{
 		/* send max number of min sized segments */
-		.tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V6,
+		.tlen = UDP_MAX_SEGMENTS,
 		.gso_len = 1,
-		.r_num_mss = UDP_MAX_SEGMENTS - CONST_HDRLEN_V6,
+		.r_num_mss = UDP_MAX_SEGMENTS,
 	},
 	{
 		/* send max number + 1 of min sized segments: fail */
-		.tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V6 + 1,
+		.tlen = UDP_MAX_SEGMENTS + 1,
 		.gso_len = 1,
 		.tfail = true,
 	},