[v3] pcapng: fix write more packets than IOV_MAX limit

diff --git a/app/test/test_pcapng.c b/app/test/test_pcapng.c
index 320dacea34..7f51946fff 100644
--- a/app/test/test_pcapng.c
+++ b/app/test/test_pcapng.c
@@ -110,7 +110,7 @@  test_setup(void)
 	}
 
 	/* Make a pool for cloned packets */
-	mp = rte_pktmbuf_pool_create_by_ops("pcapng_test_pool", NUM_PACKETS,
+	mp = rte_pktmbuf_pool_create_by_ops("pcapng_test_pool", IOV_MAX + NUM_PACKETS,
 					    0, 0,
 					    rte_pcapng_mbuf_size(pkt_len),
 					    SOCKET_ID_ANY, "ring_mp_sc");
@@ -237,6 +237,45 @@  test_validate(void)
 	return ret;
 }
 
+static int
+test_write_over_limit_iov_max(void)
+{
+	struct rte_mbuf *orig;
+	struct rte_mbuf *clones[IOV_MAX + NUM_PACKETS] = { };
+	struct dummy_mbuf mbfs;
+	unsigned int i;
+	ssize_t len;
+
+	/* make a dummy packet */
+	mbuf1_prepare(&mbfs, pkt_len);
+
+	/* clone them */
+	orig  = &mbfs.mb[0];
+	for (i = 0; i < IOV_MAX + NUM_PACKETS; i++) {
+		struct rte_mbuf *mc;
+
+		mc = rte_pcapng_copy(port_id, 0, orig, mp, pkt_len,
+				rte_get_tsc_cycles(), 0);
+		if (mc == NULL) {
+			fprintf(stderr, "Cannot copy packet\n");
+			return -1;
+		}
+		clones[i] = mc;
+	}
+
+	/* write it to capture file */
+	len = rte_pcapng_write_packets(pcapng, clones, IOV_MAX + NUM_PACKETS);
+
+	rte_pktmbuf_free_bulk(clones, IOV_MAX + NUM_PACKETS);
+
+	if (len <= 0) {
+		fprintf(stderr, "Write of packets failed\n");
+		return -1;
+	}
+
+	return 0;
+}
+
 static void
 test_cleanup(void)
 {
@@ -256,6 +295,7 @@  unit_test_suite test_pcapng_suite  = {
 		TEST_CASE(test_write_packets),
 		TEST_CASE(test_write_stats),
 		TEST_CASE(test_validate),
+		TEST_CASE(test_write_over_limit_iov_max),
 		TEST_CASES_END()
 	}
 };
diff --git a/lib/pcapng/rte_pcapng.c b/lib/pcapng/rte_pcapng.c
index 06ad712bd1..e41cf909e1 100644
--- a/lib/pcapng/rte_pcapng.c
+++ b/lib/pcapng/rte_pcapng.c
@@ -551,33 +551,16 @@  rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 	return NULL;
 }
 
-/* Count how many segments are in this array of mbufs */
-static unsigned int
-mbuf_burst_segs(struct rte_mbuf *pkts[], unsigned int n)
-{
-	unsigned int i, iovcnt;
-
-	for (iovcnt = 0, i = 0; i < n; i++) {
-		const struct rte_mbuf *m = pkts[i];
-
-		__rte_mbuf_sanity_check(m, 1);
-
-		iovcnt += m->nb_segs;
-	}
-	return iovcnt;
-}
-
 /* Write pre-formatted packets to file. */
 ssize_t
 rte_pcapng_write_packets(rte_pcapng_t *self,
 			 struct rte_mbuf *pkts[], uint16_t nb_pkts)
 {
-	int iovcnt = mbuf_burst_segs(pkts, nb_pkts);
-	struct iovec iov[iovcnt];
-	unsigned int i, cnt;
-	ssize_t ret;
+	struct iovec iov[IOV_MAX];
+	unsigned int i, cnt = 0;
+	ssize_t ret, total = 0;
 
-	for (i = cnt = 0; i < nb_pkts; i++) {
+	for (i = 0; i < nb_pkts; i++) {
 		struct rte_mbuf *m = pkts[i];
 		struct pcapng_enhance_packet_block *epb;
 
@@ -589,6 +572,20 @@  rte_pcapng_write_packets(rte_pcapng_t *self,
 			return -1;
 		}
 
+		/*
+		 * Handle case of highly fragmented and large burst size
+		 * Note: this assumes that max segments per mbuf < IOV_MAX
+		 */
+		if (unlikely(cnt + m->nb_segs >= IOV_MAX)) {
+			ret = writev(self->outfd, iov, cnt);
+			if (unlikely(ret < 0)) {
+				rte_errno = errno;
+				return -1;
+			}
+			total += ret;
+			cnt = 0;
+		}
+
 		/*
 		 * The DPDK port is recorded during pcapng_copy.
 		 * Map that to PCAPNG interface in file.
@@ -601,10 +598,12 @@  rte_pcapng_write_packets(rte_pcapng_t *self,
 		} while ((m = m->next));
 	}
 
-	ret = writev(self->outfd, iov, iovcnt);
-	if (unlikely(ret < 0))
+	ret = writev(self->outfd, iov, cnt);
+	if (unlikely(ret < 0)) {
 		rte_errno = errno;
-	return ret;
+		return -1;
+	}
+	return total + ret;
 }
 
 /* Create new pcapng writer handle */