[dpdk-stable] [PATCH v4] ip_frag: recalculate pkt length of fragment

[Yicai Lu]

In some situations, we would get several ip fragments, which total
data length is less than minimum frame(64) and padding with zeros.
Examples: Second Fragment "a0a1 a2a3 a4a5 a6a7 0000 0000 ..."
and Third Fragment "a8a9 aaab acad aeaf b0b1 b2b3 ...".
Finally, we would reassemble Second and Third Fragment like this
"a0a1 a2a3 a4a5 a6a7 0000 0000 ... a8a9 aaab acad aeaf b0b1 ...",
which is not correct!
So, we need recalculate the length of fragment to remove padding!

Fixes: 7f0983ee331c ("ip_frag: check fragment length of incoming packet")
Cc: stable at dpdk.org

Signed-off-by: Yicai Lu <luyicai at huawei.com>
---
v3 -> v4: Update the comments.
---
 lib/librte_ip_frag/rte_ipv4_reassembly.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/librte_ip_frag/rte_ipv4_reassembly.c b/lib/librte_ip_frag/rte_ipv4_reassembly.c
index 1dda8ac..fdf66a4 100644
--- a/lib/librte_ip_frag/rte_ipv4_reassembly.c
+++ b/lib/librte_ip_frag/rte_ipv4_reassembly.c
@@ -104,6 +104,7 @@ struct rte_mbuf *
 	const unaligned_uint64_t *psd;
 	uint16_t flag_offset, ip_ofs, ip_flag;
 	int32_t ip_len;
+	int32_t trim;
 
 	flag_offset = rte_be_to_cpu_16(ip_hdr->fragment_offset);
 	ip_ofs = (uint16_t)(flag_offset & RTE_IPV4_HDR_OFFSET_MASK);
@@ -117,14 +118,15 @@ struct rte_mbuf *
 
 	ip_ofs *= RTE_IPV4_HDR_OFFSET_UNITS;
 	ip_len = rte_be_to_cpu_16(ip_hdr->total_length) - mb->l3_len;
+	trim  = mb->pkt_len - (ip_len + mb->l3_len + mb->l2_len);
 
 	IP_FRAG_LOG(DEBUG, "%s:%d:\n"
-		"mbuf: %p, tms: %" PRIu64
-		", key: <%" PRIx64 ", %#x>, ofs: %u, len: %d, flags: %#x\n"
+		"mbuf: %p, tms: %" PRIu64 ", key: <%" PRIx64 ", %#x>"
+		"ofs: %u, len: %d, padding: %d, flags: %#x\n"
 		"tbl: %p, max_cycles: %" PRIu64 ", entry_mask: %#x, "
 		"max_entries: %u, use_entries: %u\n\n",
 		__func__, __LINE__,
-		mb, tms, key.src_dst[0], key.id, ip_ofs, ip_len, ip_flag,
+		mb, tms, key.src_dst[0], key.id, ip_ofs, ip_len, trim, ip_flag,
 		tbl, tbl->max_cycles, tbl->entry_mask, tbl->max_entries,
 		tbl->use_entries);
 
@@ -134,6 +136,10 @@ struct rte_mbuf *
 		return NULL;
 	}
 
+	if (unlikely(trim > 0)) {
+		rte_pktmbuf_trim(mb, trim);
+	}
+
 	/* try to find/add entry into the fragment's table. */
 	if ((fp = ip_frag_find(tbl, dr, &key, tms)) == NULL) {
 		IP_FRAG_MBUF2DR(dr, mb);
-- 
1.9.5.msysgit.1