[dpdk-dev] [PATCH v2] ip_frag: fix fragmenting IPv4 fragment

[huichao cai <chcchc88@163.com>]

Current implementation of rte_ipv4_fragment_packet() doesn’t take
into account offset and flag values of the given packet, but blindly
assumes they are always zero (original packet is not fragmented).
According to RFC791, fragment and flag values for new fragment
should take into account values provided in the original IPv4 packet.

Fixes: 4c38e5532a07 ("ip_frag: refactor IPv4 fragmentation into a proper library")
Cc: stable@dpdk.org

Signed-off-by: huichao cai <chcchc88@163.com>
---
v2:
* Reword commit message.

 lib/ip_frag/rte_ipv4_fragmentation.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/ip_frag/rte_ipv4_fragmentation.c b/lib/ip_frag/rte_ipv4_fragmentation.c
index 2e7739d..fead5a9 100644
--- a/lib/ip_frag/rte_ipv4_fragmentation.c
+++ b/lib/ip_frag/rte_ipv4_fragmentation.c
@@ -75,7 +75,7 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
 	uint32_t out_pkt_pos, in_seg_data_pos;
 	uint32_t more_in_segs;
 	uint16_t fragment_offset, flag_offset, frag_size, header_len;
-	uint16_t frag_bytes_remaining;
+	uint16_t frag_bytes_remaining, not_last_frag;
 
 	/*
 	 * Formal parameter checking.
@@ -116,7 +116,9 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
 	in_seg = pkt_in;
 	in_seg_data_pos = header_len;
 	out_pkt_pos = 0;
-	fragment_offset = 0;
+	fragment_offset = (uint16_t)((flag_offset &
+	    RTE_IPV4_HDR_OFFSET_MASK) << RTE_IPV4_HDR_FO_SHIFT);
+	not_last_frag = (uint16_t)(flag_offset & IPV4_HDR_MF_MASK);
 
 	more_in_segs = 1;
 	while (likely(more_in_segs)) {
@@ -186,7 +188,8 @@ static inline void __free_fragments(struct rte_mbuf *mb[], uint32_t num)
 
 		__fill_ipv4hdr_frag(out_hdr, in_hdr, header_len,
 		    (uint16_t)out_pkt->pkt_len,
-		    flag_offset, fragment_offset, more_in_segs);
+		    flag_offset, fragment_offset,
+		    not_last_frag || more_in_segs);
 
 		fragment_offset = (uint16_t)(fragment_offset +
 		    out_pkt->pkt_len - header_len);
-- 
1.8.3.1