pcpang changes

PATCH Superseded Stephen Hemminger 1 participant 8 messages Nov 5, 2025 – Nov 12, 2025

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Stephen Hemminger

author

2025-11-05 21:07 UTC #0 lore raw

cover pcpang changes

Fix compilation with Gcc 16 by using alloca, and add additional tests

Stephen Hemminger (2):
pcapng: use alloca instead of fixed buffer
test: add more tests for comments

 app/test/test_pcapng.c  | 18 ++++++++++++++++--
 lib/pcapng/rte_pcapng.c | 19 ++++++++++---------
 2 files changed, 26 insertions(+), 11 deletions(-)

Signature · 1 line

2.51.0

Stephen Hemminger

author

2025-11-05 21:07 UTC #1 lore raw

PATCH 1/2 pcapng: use alloca instead of fixed buffer

This is an API that accepts strings as options, and user could potentially ask for very large string as comment.
The dynamic way to fix is to use alloca() to allocate the buffer used to hold options.

Bugzilla ID: 1820

Signed-off-by Stephen Hemminger <[email protected]>

---
 lib/pcapng/rte_pcapng.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

lib/pcapng/rte_pcapng.c +10 -9

index 21bc94cea1..3067033e89 100644
@@ -34,9 +34,6 @@
 /* conversion from DPDK speed to PCAPNG */
 #define PCAPNG_MBPS_SPEED 1000000ull
 
-/* upper bound for section, stats and interface blocks (in uint32_t) */
-#define PCAPNG_BLKSIZ	(2048 / sizeof(uint32_t))
-
 /* Format of the capture file handle */
 struct rte_pcapng {
 	int  outfd;		/* output file */

@@ -145,7 +142,7 @@ pcapng_section_block(rte_pcapng_t *self,
 {
 	struct pcapng_section_header *hdr;
 	struct pcapng_option *opt;
-	uint32_t buf[PCAPNG_BLKSIZ];
+	uint32_t *buf;
 	uint32_t len;
 
 	len = sizeof(*hdr);

@@ -162,7 +159,8 @@ pcapng_section_block(rte_pcapng_t *self,
 	len += pcapng_optlen(0);
 	len += sizeof(uint32_t);
 
-	if (len > sizeof(buf))
+	buf = alloca(len);
+	if (buf == NULL)
 		return -1;
 
 	hdr = (struct pcapng_section_header *)buf;

@@ -214,7 +212,7 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 	struct pcapng_option *opt;
 	const uint8_t tsresol = 9;	/* nanosecond resolution */
 	uint32_t len;
-	uint32_t buf[PCAPNG_BLKSIZ];
+	uint32_t *buf;
 	char ifname_buf[IF_NAMESIZE];
 	char ifhw[256];
 	uint64_t speed = 0;

@@ -268,7 +266,8 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 	len += pcapng_optlen(0);
 	len += sizeof(uint32_t);
 
-	if (len > sizeof(buf))
+	buf = alloca(len);
+	if (buf == NULL)
 		return -1;
 
 	hdr = (struct pcapng_interface_block *)buf;

@@ -333,7 +332,7 @@ rte_pcapng_write_stats(rte_pcapng_t *self, uint16_t port_id,
 	uint64_t start_time = self->offset_ns;
 	uint64_t sample_time;
 	uint32_t optlen, len;
-	uint32_t buf[PCAPNG_BLKSIZ];
+	uint32_t *buf;
 
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);

@@ -353,7 +352,9 @@ rte_pcapng_write_stats(rte_pcapng_t *self, uint16_t port_id,
 		optlen += pcapng_optlen(0);
 
 	len = sizeof(*hdr) + optlen + sizeof(uint32_t);
-	if (len > sizeof(buf))
+
+	buf = alloca(len);
+	if (buf == NULL)
 		return -1;
 
 	hdr = (struct pcapng_statistics *)buf;

Signature · 1 line

2.51.0

Stephen Hemminger

author

2025-11-05 21:07 UTC #2 lore raw

PATCH 2/2 test: add more tests for comments

In reply to Stephen Hemminger

Add some more cases where comment is set in pcapng file.

Signed-off-by Stephen Hemminger <[email protected]>

---
 app/test/test_pcapng.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

app/test/test_pcapng.c +16 -2

index bcf99724fa..7e50457794 100644
@@ -162,13 +162,20 @@ fill_pcapng_file(rte_pcapng_t *pcapng, unsigned int num_packets)
 		burst_size = rte_rand_max(MAX_BURST) + 1;
 		for (i = 0; i < burst_size; i++) {
 			struct rte_mbuf *mc;
+			char *comment = NULL;
+
+			/* Put comment on one out of hundred packets */
+			if ((count + i % 100) == 0)
+				asprintf(&comment, "Function: %s\nPacket %u\n",
+					 __func__, count + i);
 
 			mc = rte_pcapng_copy(port_id, 0, orig, mp, rte_pktmbuf_pkt_len(orig),
-					     RTE_PCAPNG_DIRECTION_IN, NULL);
+					     RTE_PCAPNG_DIRECTION_IN, comment);
 			if (mc == NULL) {
 				fprintf(stderr, "Cannot copy packet\n");
 				return -1;
 			}
+			free(comment);
 			clones[i] = mc;
 		}

@@ -386,7 +393,7 @@ static int
 test_write_packets(void)
 {
 	char file_name[] = "/tmp/pcapng_test_XXXXXX.pcapng";
-	static rte_pcapng_t *pcapng;
+	rte_pcapng_t *pcapng = NULL;
 	int ret, tmp_fd, count;
 	uint64_t now = current_timestamp();

@@ -413,6 +420,13 @@ test_write_packets(void)
 		goto fail;
 	}
 
+	/* write a statistics block */
+	ret = rte_pcapng_write_stats(pcapng, port_id, 0, 0, NULL);
+	if (ret <= 0) {
+		fprintf(stderr, "Write of statistics failed\n");
+		goto fail;
+	}
+
 	count = fill_pcapng_file(pcapng, TOTAL_PACKETS);
 	if (count < 0)
 		goto fail;

Signature · 1 line

2.51.0

Stephen Hemminger

author

2025-11-12 18:14 UTC #3 lore raw

v2 cover pcapng: comment handling and tests

In reply to Stephen Hemminger

Set of changes related to pcapng. First eliminate VLA then improve handling of comment strings in packets.

v2 - chain mbuf if needed for longer comment
- add more tests

Stephen Hemminger (4):
pcapng: use alloca instead of fixed buffer
pcapng: add additional mbuf if space required on copy
test: add more tests for comments in pcapng
test: vary size of packets in pcapng test

 app/test/test_pcapng.c  | 116 +++++++++++++++++++++++++++++-----------
 lib/pcapng/rte_pcapng.c |  38 ++++++++-----
 2 files changed, 111 insertions(+), 43 deletions(-)

Signature · 1 line

2.51.0

Stephen Hemminger

author

2025-11-12 18:14 UTC #4 lore raw

PATCH v2 1/4 pcapng: use alloca instead of fixed buffer

Bugzilla ID: 1820

Signed-off-by Stephen Hemminger <[email protected]>

---
 lib/pcapng/rte_pcapng.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

lib/pcapng/rte_pcapng.c +10 -9

index 21bc94cea1..3067033e89 100644
@@ -34,9 +34,6 @@
 /* conversion from DPDK speed to PCAPNG */
 #define PCAPNG_MBPS_SPEED 1000000ull
 
-/* upper bound for section, stats and interface blocks (in uint32_t) */
-#define PCAPNG_BLKSIZ	(2048 / sizeof(uint32_t))
-
 /* Format of the capture file handle */
 struct rte_pcapng {
 	int  outfd;		/* output file */

@@ -145,7 +142,7 @@ pcapng_section_block(rte_pcapng_t *self,
 {
 	struct pcapng_section_header *hdr;
 	struct pcapng_option *opt;
-	uint32_t buf[PCAPNG_BLKSIZ];
+	uint32_t *buf;
 	uint32_t len;
 
 	len = sizeof(*hdr);

@@ -162,7 +159,8 @@ pcapng_section_block(rte_pcapng_t *self,
 	len += pcapng_optlen(0);
 	len += sizeof(uint32_t);
 
-	if (len > sizeof(buf))
+	buf = alloca(len);
+	if (buf == NULL)
 		return -1;
 
 	hdr = (struct pcapng_section_header *)buf;

@@ -214,7 +212,7 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 	struct pcapng_option *opt;
 	const uint8_t tsresol = 9;	/* nanosecond resolution */
 	uint32_t len;
-	uint32_t buf[PCAPNG_BLKSIZ];
+	uint32_t *buf;
 	char ifname_buf[IF_NAMESIZE];
 	char ifhw[256];
 	uint64_t speed = 0;

@@ -268,7 +266,8 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 	len += pcapng_optlen(0);
 	len += sizeof(uint32_t);
 
-	if (len > sizeof(buf))
+	buf = alloca(len);
+	if (buf == NULL)
 		return -1;
 
 	hdr = (struct pcapng_interface_block *)buf;

@@ -333,7 +332,7 @@ rte_pcapng_write_stats(rte_pcapng_t *self, uint16_t port_id,
 	uint64_t start_time = self->offset_ns;
 	uint64_t sample_time;
 	uint32_t optlen, len;
-	uint32_t buf[PCAPNG_BLKSIZ];
+	uint32_t *buf;
 
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);

@@ -353,7 +352,9 @@ rte_pcapng_write_stats(rte_pcapng_t *self, uint16_t port_id,
 		optlen += pcapng_optlen(0);
 
 	len = sizeof(*hdr) + optlen + sizeof(uint32_t);
-	if (len > sizeof(buf))
+
+	buf = alloca(len);
+	if (buf == NULL)
 		return -1;
 
 	hdr = (struct pcapng_statistics *)buf;

Signature · 1 line

2.51.0

Stephen Hemminger

author

2025-11-12 18:14 UTC #5 lore raw

PATCH v2 2/4 pcapng: add additional mbuf if space required on copy

In reply to Stephen Hemminger

If comment is passed to rte_pcapng_copy(), additional space maybe needed at the end of the mbuf. To handle this case generate a segmented mbuf with additional space for the options.

Signed-off-by Stephen Hemminger <[email protected]>

---
 lib/pcapng/rte_pcapng.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

lib/pcapng/rte_pcapng.c +16 -3

index 3067033e89..7c3c400c71 100644
@@ -540,11 +540,24 @@ rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 	if (comment)
 		optlen += pcapng_optlen(strlen(comment));
 
-	/* reserve trailing options and block length */
+	/*
+	 * Try to put options at the end of this mbuf.
+	 * If not use an mbuf chain.
+	 */
 	opt = (struct pcapng_option *)
 		rte_pktmbuf_append(mc, optlen + sizeof(uint32_t));
-	if (unlikely(opt == NULL))
-		goto fail;
+	if (unlikely(opt == NULL)) {
+		struct rte_mbuf *ml = rte_pktmbuf_alloc(mp);
+
+		if (unlikely(ml == NULL))
+			goto fail;
+
+		opt = (struct pcapng_option *)rte_pktmbuf_append(ml, optlen + sizeof(uint32_t));
+		if (unlikely(opt == NULL || rte_pktmbuf_chain(mc, ml) != 0)) {
+			rte_pktmbuf_free(ml);
+			goto fail;
+		}
+	}
 
 	switch (direction) {
 	case RTE_PCAPNG_DIRECTION_IN:

Signature · 1 line

2.51.0

Stephen Hemminger

author

2025-11-12 18:14 UTC #6 lore raw

PATCH v2 3/4 test: add more tests for comments in pcapng

In reply to Stephen Hemminger

Add some more cases where comment is set in pcapng file.

Signed-off-by Stephen Hemminger <[email protected]>

---
 app/test/test_pcapng.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

app/test/test_pcapng.c +22 -4

index bcf99724fa..f2b49c31c7 100644
@@ -125,8 +125,7 @@ test_setup(void)
 
 	/* Make a pool for cloned packets */
 	mp = rte_pktmbuf_pool_create_by_ops("pcapng_test_pool",
-					    MAX_BURST * 32, 0, 0,
-					    rte_pcapng_mbuf_size(pkt_len) + 128,
+					    MAX_BURST * 32, 0, 0, rte_pcapng_mbuf_size(pkt_len),
 					    SOCKET_ID_ANY, "ring_mp_sc");
 	if (mp == NULL) {
 		fprintf(stderr, "Cannot create mempool\n");

@@ -149,6 +148,13 @@ fill_pcapng_file(rte_pcapng_t *pcapng, unsigned int num_packets)
 	unsigned int burst_size;
 	unsigned int count;
 	ssize_t len;
+	const char *examples[] = {
+		"EAL init complete. May the cores be ever in your favor.",
+		"No packets were harmed in the making of this burst.",
+		"rte_eth_dev_start(): crossing fingers and enabling queues...",
+		"Congratulations, you’ve reached the end of the RX path. Please collect your free cache miss.",
+		"Lockless and fearless — that’s how we roll in userspace."
+	};
 
 	/* make a dummy packet */
 	mbuf1_prepare(&mbfs, pkt_len);

@@ -162,9 +168,14 @@ fill_pcapng_file(rte_pcapng_t *pcapng, unsigned int num_packets)
 		burst_size = rte_rand_max(MAX_BURST) + 1;
 		for (i = 0; i < burst_size; i++) {
 			struct rte_mbuf *mc;
+			const char *comment = NULL;
+
+			/* Put comment on occasional packets */
+			if ((count + i) % 42 == 0)
+				comment = examples[rte_rand_max(RTE_DIM(examples))];
 
 			mc = rte_pcapng_copy(port_id, 0, orig, mp, rte_pktmbuf_pkt_len(orig),
-					     RTE_PCAPNG_DIRECTION_IN, NULL);
+					     RTE_PCAPNG_DIRECTION_IN, comment);
 			if (mc == NULL) {
 				fprintf(stderr, "Cannot copy packet\n");
 				return -1;

@@ -386,7 +397,7 @@ static int
 test_write_packets(void)
 {
 	char file_name[] = "/tmp/pcapng_test_XXXXXX.pcapng";
-	static rte_pcapng_t *pcapng;
+	rte_pcapng_t *pcapng = NULL;
 	int ret, tmp_fd, count;
 	uint64_t now = current_timestamp();

@@ -413,6 +424,13 @@ test_write_packets(void)
 		goto fail;
 	}
 
+	/* write a statistics block */
+	ret = rte_pcapng_write_stats(pcapng, port_id, 0, 0, NULL);
+	if (ret <= 0) {
+		fprintf(stderr, "Write of statistics failed\n");
+		goto fail;
+	}
+
 	count = fill_pcapng_file(pcapng, TOTAL_PACKETS);
 	if (count < 0)
 		goto fail;

Signature · 1 line

2.51.0

Stephen Hemminger

author

2025-11-12 18:14 UTC #7 lore raw

PATCH v2 4/4 test: vary size of packets in pcapng test

In reply to Stephen Hemminger

In order exercise more logic in pcapng, vary the size of the packets.

Signed-off-by Stephen Hemminger <[email protected]>

---
 app/test/test_pcapng.c | 94 +++++++++++++++++++++++++++++-------------
 1 file changed, 65 insertions(+), 29 deletions(-)

app/test/test_pcapng.c +65 ~~-29~~

index f2b49c31c7..5010355df5 100644
@@ -28,10 +28,9 @@
 #define TOTAL_PACKETS	4096
 #define MAX_BURST	64
 #define MAX_GAP_US	100000
-#define DUMMY_MBUF_NUM	3
+#define DUMMY_MBUF_NUM	2
 
 static struct rte_mempool *mp;
-static const uint32_t pkt_len = 200;
 static uint16_t port_id;
 static const char null_dev[] = "net_null0";

@@ -41,13 +40,36 @@ struct dummy_mbuf {
 	uint8_t buf[DUMMY_MBUF_NUM][RTE_MBUF_DEFAULT_BUF_SIZE];
 };
 
+#define MAX_DATA_SIZE (RTE_MBUF_DEFAULT_BUF_SIZE - RTE_PKTMBUF_HEADROOM)
+
+/* RFC 864 chargen pattern used for comment testing */
+#define FILL_LINE_LENGTH 72
+#define FILL_START	0x21 /* ! */
+#define FILL_END	0x7e /* ~ */
+#define FILL_RANGE	(FILL_END - FILL_START)
+
 static void
-dummy_mbuf_prep(struct rte_mbuf *mb, uint8_t buf[], uint32_t buf_len,
-	uint32_t data_len)
+fill_mbuf(struct rte_mbuf *mb)
 {
-	uint32_t i;
-	uint8_t *db;
+	unsigned int len = rte_pktmbuf_tailroom(mb);
+	char *buf = rte_pktmbuf_append(mb, len);
+	unsigned int n = 0;
+
+	while (n < len - 1) {
+		char ch = FILL_START + (n % FILL_LINE_LENGTH) % FILL_RANGE;
+		for (unsigned int i = 0; i < FILL_LINE_LENGTH && n < len - 1; i++) {
+			buf[n++] = ch;
+			if (++ch == FILL_END)
+				ch = FILL_START;
+		}
+		if (n < len - 1)
+			buf[n++] = '\n';
+	}
+}
 
+static void
+dummy_mbuf_prep(struct rte_mbuf *mb, uint8_t buf[], uint32_t buf_len)
+{
 	mb->buf_addr = buf;
 	rte_mbuf_iova_set(mb, (uintptr_t)buf);
 	mb->buf_len = buf_len;

@@ -57,15 +79,11 @@ dummy_mbuf_prep(struct rte_mbuf *mb, uint8_t buf[], uint32_t buf_len,
 	mb->pool = (void *)buf;
 
 	rte_pktmbuf_reset(mb);
-	db = (uint8_t *)rte_pktmbuf_append(mb, data_len);
-
-	for (i = 0; i != data_len; i++)
-		db[i] = i;
 }
 
 /* Make an IP packet consisting of chain of one packets */
 static void
-mbuf1_prepare(struct dummy_mbuf *dm, uint32_t plen)
+mbuf1_prepare(struct dummy_mbuf *dm)
 {
 	struct {
 		struct rte_ether_hdr eth;

@@ -84,32 +102,47 @@ mbuf1_prepare(struct dummy_mbuf *dm, uint32_t plen)
 			.dst_addr = rte_cpu_to_be_32(RTE_IPV4_BROADCAST),
 		},
 		.udp = {
+			.src_port = rte_cpu_to_be_16(19), /* Chargen port */
 			.dst_port = rte_cpu_to_be_16(9), /* Discard port */
 		},
 	};
 
 	memset(dm, 0, sizeof(*dm));
-	dummy_mbuf_prep(&dm->mb[0], dm->buf[0], sizeof(dm->buf[0]), plen);
+	dummy_mbuf_prep(&dm->mb[0], dm->buf[0], sizeof(dm->buf[0]));
+	dummy_mbuf_prep(&dm->mb[1], dm->buf[1], sizeof(dm->buf[1]));
 
 	rte_eth_random_addr(pkt.eth.src_addr.addr_bytes);
-	plen -= sizeof(struct rte_ether_hdr);
+	memcpy(rte_pktmbuf_append(&dm->mb[0], sizeof(pkt)), &pkt, sizeof(pkt));
+
+	fill_mbuf(&dm->mb[1]);
+	rte_pktmbuf_chain(&dm->mb[0], &dm->mb[1]);
+
+	rte_mbuf_sanity_check(&dm->mb[0], 1);
+	rte_mbuf_sanity_check(&dm->mb[1], 0);
+}
 
-	pkt.ip.total_length = rte_cpu_to_be_16(plen);
-	pkt.ip.hdr_checksum = rte_ipv4_cksum(&pkt.ip);
+static void
+mbuf1_resize(struct dummy_mbuf *dm, uint16_t len)
+{
+	struct {
+		struct rte_ether_hdr eth;
+		struct rte_ipv4_hdr ip;
+		struct rte_udp_hdr udp;
+	} *pkt = rte_pktmbuf_mtod(&dm->mb[0], void *);
 
-	plen -= sizeof(struct rte_ipv4_hdr);
-	pkt.udp.src_port = rte_rand();
-	pkt.udp.dgram_len = rte_cpu_to_be_16(plen);
+	dm->mb[1].data_len = len;
+	dm->mb[0].pkt_len = dm->mb[0].data_len + dm->mb[1].data_len;
 
-	memcpy(rte_pktmbuf_mtod(dm->mb, void *), &pkt, sizeof(pkt));
+	len += sizeof(struct rte_udp_hdr);
+	pkt->udp.dgram_len = rte_cpu_to_be_16(len);
 
-	/* 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]);
+	len += sizeof(struct rte_ipv4_hdr);
+	pkt->ip.total_length = rte_cpu_to_be_16(len);
+	pkt->ip.hdr_checksum = 0;
+	pkt->ip.hdr_checksum = rte_ipv4_cksum(&pkt->ip);
+
+	rte_mbuf_sanity_check(&dm->mb[0], 1);
+	rte_mbuf_sanity_check(&dm->mb[1], 0);
 }
 
 static int

@@ -125,7 +158,8 @@ test_setup(void)
 
 	/* Make a pool for cloned packets */
 	mp = rte_pktmbuf_pool_create_by_ops("pcapng_test_pool",
-					    MAX_BURST * 32, 0, 0, rte_pcapng_mbuf_size(pkt_len),
+					    MAX_BURST * 32, 0, 0,
+					    rte_pcapng_mbuf_size(MAX_DATA_SIZE),
 					    SOCKET_ID_ANY, "ring_mp_sc");
 	if (mp == NULL) {
 		fprintf(stderr, "Cannot create mempool\n");

@@ -156,8 +190,7 @@ fill_pcapng_file(rte_pcapng_t *pcapng, unsigned int num_packets)
 		"Lockless and fearless — that’s how we roll in userspace."
 	};
 
-	/* make a dummy packet */
-	mbuf1_prepare(&mbfs, pkt_len);
+	mbuf1_prepare(&mbfs);
 	orig  = &mbfs.mb[0];
 
 	for (count = 0; count < num_packets; count += burst_size) {

@@ -174,6 +207,9 @@ fill_pcapng_file(rte_pcapng_t *pcapng, unsigned int num_packets)
 			if ((count + i) % 42 == 0)
 				comment = examples[rte_rand_max(RTE_DIM(examples))];
 
+			/* Vary the size of the packets */
+			mbuf1_resize(&mbfs, rte_rand_max(MAX_DATA_SIZE));
+
 			mc = rte_pcapng_copy(port_id, 0, orig, mp, rte_pktmbuf_pkt_len(orig),
 					     RTE_PCAPNG_DIRECTION_IN, comment);
 			if (mc == NULL) {

Signature · 1 line

2.51.0