[PATCH] app/dumpcap: fix handling of jumbo frames

[Stephen Hemminger <stephen@networkplumber.org>]

If dumpcap (in legacy pcap mode) tried to handle a large segmented
frame it would core dump because rte_pktmbuf_read() would return NULL.
Fix by using same logic as in pcap PMD.

Fixes: cbb44143be74 ("app/dumpcap: add new packet capture application")
Reported-by: Tianli Lai <laitianli@tom.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---

 app/dumpcap/main.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/app/dumpcap/main.c b/app/dumpcap/main.c
index 6feb8f5672..fcfaa19951 100644
--- a/app/dumpcap/main.c
+++ b/app/dumpcap/main.c
@@ -902,7 +902,7 @@ static ssize_t
 pcap_write_packets(pcap_dumper_t *dumper,
 		   struct rte_mbuf *pkts[], uint16_t n)
 {
-	uint8_t temp_data[RTE_MBUF_DEFAULT_BUF_SIZE];
+	uint8_t temp_data[RTE_ETHER_MAX_JUMBO_FRAME_LEN];
 	struct pcap_pkthdr header;
 	uint16_t i;
 	size_t total = 0;
@@ -911,14 +911,19 @@ pcap_write_packets(pcap_dumper_t *dumper,
 
 	for (i = 0; i < n; i++) {
 		struct rte_mbuf *m = pkts[i];
+		size_t len, caplen;
 
-		header.len = rte_pktmbuf_pkt_len(m);
-		header.caplen = RTE_MIN(header.len, sizeof(temp_data));
+		len = caplen = rte_pktmbuf_pkt_len(m);
+		if (unlikely(!rte_pktmbuf_is_contiguous(m) && len > sizeof(temp_data)))
+			caplen = sizeof(temp_data);
+
+		header.len = len;
+		header.caplen = caplen;
 
 		pcap_dump((u_char *)dumper, &header,
-			  rte_pktmbuf_read(m, 0, header.caplen, temp_data));
+			  rte_pktmbuf_read(m, 0, caplen, temp_data));
 
-		total += sizeof(header) + header.len;
+		total += sizeof(header) + caplen;
 	}
 
 	return total;
-- 
2.45.2