net/mlx5e: Fix selftest for small MTUs

Loopback test had fixed packet size, which can be bigger than configured
MTU. Shorten the loopback packet size to be bigger than minimal MTU
allowed by the device. Text field removed from struct 'mlx5ehdr'
as redundant to allow send small packets as minimal allowed MTU.

Fixes: d605d668 ("net/mlx5e: Add support for ethtool self diagnostics test")
Signed-off-by: Valentine Fatiev <valentinef@mellanox.com>
Reviewed-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_selftest.c

@@ -98,18 +98,17 @@ static int mlx5e_test_link_speed(struct mlx5e_priv *priv)
 	return 1;
 }
 
-#ifdef CONFIG_INET
-/* loopback test */
-#define MLX5E_TEST_PKT_SIZE (MLX5E_RX_MAX_HEAD - NET_IP_ALIGN)
-static const char mlx5e_test_text[ETH_GSTRING_LEN] = "MLX5E SELF TEST";
-#define MLX5E_TEST_MAGIC 0x5AEED15C001ULL
-
 struct mlx5ehdr {
 	__be32 version;
 	__be64 magic;
-	char   text[ETH_GSTRING_LEN];
 };
 
+#ifdef CONFIG_INET
+/* loopback test */
+#define MLX5E_TEST_PKT_SIZE (sizeof(struct ethhdr) + sizeof(struct iphdr) +\
+			     sizeof(struct udphdr) + sizeof(struct mlx5ehdr))
+#define MLX5E_TEST_MAGIC 0x5AEED15C001ULL
+
 static struct sk_buff *mlx5e_test_get_udp_skb(struct mlx5e_priv *priv)
 {
 	struct sk_buff *skb = NULL;
@@ -117,10 +116,7 @@ static struct sk_buff *mlx5e_test_get_udp_skb(struct mlx5e_priv *priv)
 	struct ethhdr *ethh;
 	struct udphdr *udph;
 	struct iphdr *iph;
-	int datalen, iplen;
-
-	datalen = MLX5E_TEST_PKT_SIZE -
-		  (sizeof(*ethh) + sizeof(*iph) + sizeof(*udph));
+	int    iplen;
 
 	skb = netdev_alloc_skb(priv->netdev, MLX5E_TEST_PKT_SIZE);
 	if (!skb) {
@@ -149,7 +145,7 @@ static struct sk_buff *mlx5e_test_get_udp_skb(struct mlx5e_priv *priv)
 	/* Fill UDP header */
 	udph->source = htons(9);
 	udph->dest = htons(9); /* Discard Protocol */
-	udph->len = htons(datalen + sizeof(struct udphdr));
+	udph->len = htons(sizeof(struct mlx5ehdr) + sizeof(struct udphdr));
 	udph->check = 0;
 
 	/* Fill IP header */
@@ -157,7 +153,8 @@ static struct sk_buff *mlx5e_test_get_udp_skb(struct mlx5e_priv *priv)
 	iph->ttl = 32;
 	iph->version = 4;
 	iph->protocol = IPPROTO_UDP;
-	iplen = sizeof(struct iphdr) + sizeof(struct udphdr) + datalen;
+	iplen = sizeof(struct iphdr) + sizeof(struct udphdr) +
+		sizeof(struct mlx5ehdr);
 	iph->tot_len = htons(iplen);
 	iph->frag_off = 0;
 	iph->saddr = 0;
@@ -170,9 +167,6 @@ static struct sk_buff *mlx5e_test_get_udp_skb(struct mlx5e_priv *priv)
 	mlxh = skb_put(skb, sizeof(*mlxh));
 	mlxh->version = 0;
 	mlxh->magic = cpu_to_be64(MLX5E_TEST_MAGIC);
-	strlcpy(mlxh->text, mlx5e_test_text, sizeof(mlxh->text));
-	datalen -= sizeof(*mlxh);
-	skb_put_zero(skb, datalen);
 
 	skb->csum = 0;
 	skb->ip_summed = CHECKSUM_PARTIAL;