selftests: xsk: do not send zero-length packets

Do not try to send packets of zero length since they are dropped by
veth after commit 726e2c59 ("veth: Ensure eth header is in skb's
linear part"). Replace these two packets with packets of length 60 so
that they are not dropped.

Also clean up the confusing naming. MIN_PKT_SIZE was really
MIN_ETH_PKT_SIZE and PKT_SIZE was both MIN_ETH_SIZE and the default
packet size called just PKT_SIZE. Make it consistent by using the
right define in the right place.
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/r/20220510115604.8717-3-magnus.karlsson@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/xdpxceiver.c

@@ -575,7 +575,7 @@ static struct pkt *pkt_generate(struct ifobject *ifobject, u32 pkt_nb)
 
 	if (!pkt)
 		return NULL;
-	if (!pkt->valid || pkt->len < PKT_SIZE)
+	if (!pkt->valid || pkt->len < MIN_PKT_SIZE)
 		return pkt;
 
 	data = xsk_umem__get_data(ifobject->umem->buffer, pkt->addr);
@@ -677,8 +677,8 @@ static bool is_pkt_valid(struct pkt *pkt, void *buffer, u64 addr, u32 len)
 		return false;
 	}
 
-	if (len < PKT_SIZE) {
-		/*Do not try to verify packets that are smaller than minimum size. */
+	if (len < MIN_PKT_SIZE || pkt->len < MIN_PKT_SIZE) {
+		/* Do not try to verify packets that are smaller than minimum size. */
 		return true;
 	}
 
@@ -1282,10 +1282,10 @@ static void testapp_single_pkt(struct test_spec *test)
 static void testapp_invalid_desc(struct test_spec *test)
 {
 	struct pkt pkts[] = {
-		/* Zero packet length at address zero allowed */
-		{0, 0, 0, true},
-		/* Zero packet length allowed */
-		{0x1000, 0, 0, true},
+		/* Zero packet address allowed */
+		{0, PKT_SIZE, 0, true},
+		/* Allowed packet */
+		{0x1000, PKT_SIZE, 0, true},
 		/* Straddling the start of umem */
 		{-2, PKT_SIZE, 0, false},
 		/* Packet too large */

tools/testing/selftests/bpf/xdpxceiver.h

@@ -25,9 +25,10 @@
 #define MAX_TEARDOWN_ITER 10
 #define PKT_HDR_SIZE (sizeof(struct ethhdr) + sizeof(struct iphdr) + \
 			sizeof(struct udphdr))
-#define MIN_PKT_SIZE 64
+#define MIN_ETH_PKT_SIZE 64
 #define ETH_FCS_SIZE 4
-#define PKT_SIZE (MIN_PKT_SIZE - ETH_FCS_SIZE)
+#define MIN_PKT_SIZE (MIN_ETH_PKT_SIZE - ETH_FCS_SIZE)
+#define PKT_SIZE (MIN_PKT_SIZE)
 #define IP_PKT_SIZE (PKT_SIZE - sizeof(struct ethhdr))
 #define IP_PKT_VER 0x4
 #define IP_PKT_TOS 0x9