[dpdk-dev] [PATCH v2] gso: fix pyld_unit_size issue for udp gso

[yang_y_yi@163.com]

From: Yi Yang <yangyi01@inspur.com>

Fragment offset of IPv4 header is measured in units of
8 bytes. Fragment offset of UDP fragments will be wrong
after GSO if pyld_unit_size isn't multiple of 8. Say
pyld_unit_size is 1500, fragment offset of the second
UDP fragment will be 187 (i.e. 1500 / 8), which means 1496,
and it will result in 4-byte data loss (1500 - 1496 = 4).
So UDP GRO will reassemble out a wrong packet.

Fixes: b166d4f30b66 ("gso: support UDP/IPv4 fragmentation")

Signed-off-by: Yi Yang <yangyi01@inspur.com>
---
 lib/librte_gso/gso_udp4.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/librte_gso/gso_udp4.c b/lib/librte_gso/gso_udp4.c
index 21fea09..6fa68f2 100644
--- a/lib/librte_gso/gso_udp4.c
+++ b/lib/librte_gso/gso_udp4.c
@@ -69,7 +69,10 @@
 		return 1;
 	}
 
-	pyld_unit_size = gso_size - hdr_offset;
+	/* pyld_unit_size must be a multiple of 8 because frag_off
+	 * uses 8 bytes as unit.
+	 */
+	pyld_unit_size = (gso_size - hdr_offset) & ~7U;
 
 	/* Segment the payload */
 	ret = gso_do_segment(pkt, hdr_offset, pyld_unit_size, direct_pool,
-- 
1.8.3.1