xsk: discard zero length descriptors in Tx path

Descriptors with zero length are not supported by many NICs. To preserve
uniform behavior discard any zero length desc as invvalid desc.
Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@intel.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/r/20230719132421.584801-10-maciej.fijalkowski@intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

net/xdp/xsk_queue.h

@@ -140,6 +140,9 @@ static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
 {
 	u64 offset = desc->addr & (pool->chunk_size - 1);
 
+	if (!desc->len)
+		return false;
+
 	if (offset + desc->len > pool->chunk_size)
 		return false;
 
@@ -156,6 +159,9 @@ static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool,
 {
 	u64 addr = xp_unaligned_add_offset_to_addr(desc->addr);
 
+	if (!desc->len)
+		return false;
+
 	if (desc->len > pool->chunk_size)
 		return false;