[PATCH 22.11] pcapng: fix handling of chained mbufs

[PATCH 22.11] pcapng: fix handling of chained mbufs

[Oleksandr Nahnybida]

[ upstream commit 6db358536fee7891b5cb670df94ec87543ddd0fb ]

The pcapng generates corrupted files when dealing with chained mbufs.
This issue arises because in rte_pcapng_copy the length of the EPB block
is incorrectly calculated using the data_len of the first mbuf instead
of the pkt_len, despite that rte_pcapng_write_packets correctly writing
the mbuf chain to disk.

This fix ensures that the block length is calculated based on the pkt_len,
aligning it with the actual data written to disk.

Fixes: 8d23ce8f5ee9 ("pcapng: add new library for writing pcapng files")

Signed-off-by: Oleksandr Nahnybida <oleksandrn@interfacemasters.com>
---
 app/test/test_pcapng.c  | 10 +++++++++-
 lib/pcapng/rte_pcapng.c | 12 ++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/app/test/test_pcapng.c b/app/test/test_pcapng.c
index a7acbdc058..e9c85f2e02 100644
--- a/app/test/test_pcapng.c
+++ b/app/test/test_pcapng.c
@@ -81,6 +81,14 @@ mbuf1_prepare(struct dummy_mbuf *dm, uint32_t plen)

 	rte_eth_random_addr(pkt.eth.src_addr.addr_bytes);
 	memcpy(rte_pktmbuf_mtod(dm->mb, void *), &pkt, RTE_MIN(sizeof(pkt), plen));
+
+	/* Idea here is to create mbuf chain big enough that after mbuf deep copy they won't be
+	 * compressed into single mbuf to properly test store of chained mbufs
+	 */
+	dummy_mbuf_prep(&dm->mb[1], dm->buf[1], sizeof(dm->buf[1]), pkt_len);
+	dummy_mbuf_prep(&dm->mb[2], dm->buf[2], sizeof(dm->buf[2]), pkt_len);
+	rte_pktmbuf_chain(&dm->mb[0], &dm->mb[1]);
+	rte_pktmbuf_chain(&dm->mb[0], &dm->mb[2]);
 }

 static int
@@ -138,7 +146,7 @@ test_write_packets(void)
 	for (i = 0; i < NUM_PACKETS; i++) {
 		struct rte_mbuf *mc;

-		mc = rte_pcapng_copy(port_id, 0, orig, mp, pkt_len,
+		mc = rte_pcapng_copy(port_id, 0, orig, mp, rte_pktmbuf_pkt_len(orig),
 				rte_get_tsc_cycles(), 0);
 		if (mc == NULL) {
 			fprintf(stderr, "Cannot copy packet\n");
diff --git a/lib/pcapng/rte_pcapng.c b/lib/pcapng/rte_pcapng.c
index d8fd36799b..3f5e08379a 100644
--- a/lib/pcapng/rte_pcapng.c
+++ b/lib/pcapng/rte_pcapng.c
@@ -454,7 +454,7 @@ rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 		enum rte_pcapng_direction direction)
 {
 	struct pcapng_enhance_packet_block *epb;
-	uint32_t orig_len, data_len, padding, flags;
+	uint32_t orig_len, pkt_len, padding, flags;
 	struct pcapng_option *opt;
 	uint16_t optlen;
 	struct rte_mbuf *mc;
@@ -497,8 +497,8 @@ rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 		    (md->ol_flags & RTE_MBUF_F_RX_RSS_HASH));

 	/* pad the packet to 32 bit boundary */
-	data_len = rte_pktmbuf_data_len(mc);
-	padding = RTE_ALIGN(data_len, sizeof(uint32_t)) - data_len;
+	pkt_len = rte_pktmbuf_pkt_len(mc);
+	padding = RTE_ALIGN(pkt_len, sizeof(uint32_t)) - pkt_len;
 	if (padding > 0) {
 		void *tail = rte_pktmbuf_append(mc, padding);

@@ -558,14 +558,14 @@ rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 		goto fail;

 	epb->block_type = PCAPNG_ENHANCED_PACKET_BLOCK;
-	epb->block_length = rte_pktmbuf_data_len(mc);
+	epb->block_length = rte_pktmbuf_pkt_len(mc);

 	/* Interface index is filled in later during write */
 	mc->port = port_id;

 	epb->timestamp_hi = ns >> 32;
 	epb->timestamp_lo = (uint32_t)ns;
-	epb->capture_length = data_len;
+	epb->capture_length = pkt_len;
 	epb->original_length = orig_len;

 	/* set trailer of block length */
@@ -594,7 +594,7 @@ rte_pcapng_write_packets(rte_pcapng_t *self,
 		/* sanity check that is really a pcapng mbuf */
 		epb = rte_pktmbuf_mtod(m, struct pcapng_enhance_packet_block *);
 		if (unlikely(epb->block_type != PCAPNG_ENHANCED_PACKET_BLOCK ||
-			     epb->block_length != rte_pktmbuf_data_len(m))) {
+			     epb->block_length != rte_pktmbuf_pkt_len(m))) {
 			rte_errno = EINVAL;
 			return -1;
 		}
--
2.47.0

Re: [PATCH 22.11] pcapng: fix handling of chained mbufs

[Luca Boccassi]

On Mon, 28 Oct 2024 at 14:03, Oleksandr Nahnybida
<oleksandrn@interfacemasters.com> wrote:
>
> [ upstream commit 6db358536fee7891b5cb670df94ec87543ddd0fb ]
>
> The pcapng generates corrupted files when dealing with chained mbufs.
> This issue arises because in rte_pcapng_copy the length of the EPB block
> is incorrectly calculated using the data_len of the first mbuf instead
> of the pkt_len, despite that rte_pcapng_write_packets correctly writing
> the mbuf chain to disk.
>
> This fix ensures that the block length is calculated based on the pkt_len,
> aligning it with the actual data written to disk.
>
> Fixes: 8d23ce8f5ee9 ("pcapng: add new library for writing pcapng files")
>
> Signed-off-by: Oleksandr Nahnybida <oleksandrn@interfacemasters.com>
> ---
>  app/test/test_pcapng.c  | 10 +++++++++-
>  lib/pcapng/rte_pcapng.c | 12 ++++++------
>  2 files changed, 15 insertions(+), 7 deletions(-)

Thanks, applied