[PATCH v1] pcapng: allow any protocol link type for the interface block

[PATCH v1] pcapng: allow any protocol link type for the interface block

[Schneide]

From: Dylan Schneider <schneide@qti.qualcomm.com>

Allow the user to specify protocol link type when creating pcapng files.
This change is needed to specify the protocol type in the pcapng file,
DLT_EN10MB specifies ethernet packets only. This will allow dissectors
for other protocols to be used on files generated by pcapng.

Includes a breaking change to rte_pcapng_add_interface to add link_type
parameter. Existing calls to the function have been updated to pass
DLT_EN10MB for the link type argument.

Fixes: d1da6d0d04c7 ("pcapng: require per-interface information")
Signed-off-by: Dylan Schneider <schneide@qti.qualcomm.com>
Cc: stephen@networkplumber.org
---
 .mailmap                               |  1 +
 app/dumpcap/main.c                     |  5 +++--
 app/test/test_pcapng.c                 |  8 ++++----
 doc/guides/rel_notes/release_25_11.rst |  4 ++++
 lib/graph/graph_pcap.c                 |  2 +-
 lib/pcapng/meson.build                 |  2 ++
 lib/pcapng/rte_pcapng.c                | 21 +++++++++++++++------
 lib/pcapng/rte_pcapng.h                |  7 ++++++-
 8 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/.mailmap b/.mailmap
index 34a99f93a1..1a003778b2 100644
--- a/.mailmap
+++ b/.mailmap
@@ -402,6 +402,7 @@ Dukai Yuan <dukaix.yuan@intel.com>
 Dumitru Ceara <dceara@redhat.com> <dumitru.ceara@gmail.com>
 Duncan Bellamy <dunk@denkimushi.com>
 Dustin Lundquist <dustin@null-ptr.net>
+Dylan Schneider <schneide@qti.qualcomm.com>
 Dzmitry Sautsa <dzmitryx.sautsa@intel.com>
 Ed Czeck <ed.czeck@atomicrules.com>
 Eduard Serra <eserra@vmware.com>
diff --git a/app/dumpcap/main.c b/app/dumpcap/main.c
index 3d3c0dbc66..e5ba36350b 100644
--- a/app/dumpcap/main.c
+++ b/app/dumpcap/main.c
@@ -800,8 +800,9 @@ static dumpcap_out_t create_output(void)
 		free(os);
 
 		TAILQ_FOREACH(intf, &interfaces, next) {
-			if (rte_pcapng_add_interface(ret.pcapng, intf->port, intf->ifname,
-						     intf->ifdescr, intf->opts.filter) < 0)
+			if (rte_pcapng_add_interface(ret.pcapng, intf->port, DLT_EN10MB,
+						     intf->ifname, intf->ifdescr,
+						     intf->opts.filter) < 0)
 				rte_exit(EXIT_FAILURE, "rte_pcapng_add_interface %u failed\n",
 					intf->port);
 		}
diff --git a/app/test/test_pcapng.c b/app/test/test_pcapng.c
index 8f2cff36c3..bcf99724fa 100644
--- a/app/test/test_pcapng.c
+++ b/app/test/test_pcapng.c
@@ -345,7 +345,7 @@ test_add_interface(void)
 	}
 
 	/* Add interface to the file */
-	ret = rte_pcapng_add_interface(pcapng, port_id,
+	ret = rte_pcapng_add_interface(pcapng, port_id, DLT_EN10MB,
 				       NULL, NULL, NULL);
 	if (ret < 0) {
 		fprintf(stderr, "can not add port %u\n", port_id);
@@ -353,7 +353,7 @@ test_add_interface(void)
 	}
 
 	/* Add interface with ifname and ifdescr */
-	ret = rte_pcapng_add_interface(pcapng, port_id,
+	ret = rte_pcapng_add_interface(pcapng, port_id, DLT_EN10MB,
 				       "myeth", "Some long description", NULL);
 	if (ret < 0) {
 		fprintf(stderr, "can not add port %u with ifname\n", port_id);
@@ -361,7 +361,7 @@ test_add_interface(void)
 	}
 
 	/* Add interface with filter */
-	ret = rte_pcapng_add_interface(pcapng, port_id,
+	ret = rte_pcapng_add_interface(pcapng, port_id, DLT_EN10MB,
 				       NULL, NULL, "tcp port 8080");
 	if (ret < 0) {
 		fprintf(stderr, "can not add port %u with filter\n", port_id);
@@ -406,7 +406,7 @@ test_write_packets(void)
 	}
 
 	/* Add interface to the file */
-	ret = rte_pcapng_add_interface(pcapng, port_id,
+	ret = rte_pcapng_add_interface(pcapng, port_id, DLT_EN10MB,
 				       NULL, NULL, NULL);
 	if (ret < 0) {
 		fprintf(stderr, "can not add port %u\n", port_id);
diff --git a/doc/guides/rel_notes/release_25_11.rst b/doc/guides/rel_notes/release_25_11.rst
index ccad6d89ff..b1f75a489c 100644
--- a/doc/guides/rel_notes/release_25_11.rst
+++ b/doc/guides/rel_notes/release_25_11.rst
@@ -84,6 +84,10 @@ API Changes
    Also, make sure to start the actual text at the margin.
    =======================================================
 
+* pcapng: Changed the API for adding interfaces to include a link type argument.
+  The link type was previously hardcoded to the ethernet link type in the API.
+  This argument is added to ``rte_pcapng_add_interface``.
+  These functions are versioned to retain binary compatibility until the next LTS release.
 
 ABI Changes
 -----------
diff --git a/lib/graph/graph_pcap.c b/lib/graph/graph_pcap.c
index 89525f1220..08dcda0d28 100644
--- a/lib/graph/graph_pcap.c
+++ b/lib/graph/graph_pcap.c
@@ -117,7 +117,7 @@ graph_pcap_file_open(const char *filename)
 
 	/* Add the configured interfaces as possible capture ports */
 	RTE_ETH_FOREACH_DEV(portid) {
-		ret = rte_pcapng_add_interface(pcapng_fd, portid,
+		ret = rte_pcapng_add_interface(pcapng_fd, portid, DLT_EN10MB,
 					       NULL, NULL, NULL);
 		if (ret < 0) {
 			graph_err("Graph rte_pcapng_add_interface port %u failed: %d",
diff --git a/lib/pcapng/meson.build b/lib/pcapng/meson.build
index 4549925d41..3aa7ba5155 100644
--- a/lib/pcapng/meson.build
+++ b/lib/pcapng/meson.build
@@ -5,3 +5,5 @@ sources = files('rte_pcapng.c')
 headers = files('rte_pcapng.h')
 
 deps += ['ethdev']
+
+use_function_versioning = true
diff --git a/lib/pcapng/rte_pcapng.c b/lib/pcapng/rte_pcapng.c
index 2a07b4c1f5..1ff8d14d08 100644
--- a/lib/pcapng/rte_pcapng.c
+++ b/lib/pcapng/rte_pcapng.c
@@ -200,11 +200,10 @@ pcapng_section_block(rte_pcapng_t *self,
 }
 
 /* Write an interface block for a DPDK port */
-RTE_EXPORT_SYMBOL(rte_pcapng_add_interface)
-int
-rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port,
-			 const char *ifname, const char *ifdescr,
-			 const char *filter)
+RTE_DEFAULT_SYMBOL(27, int, rte_pcapng_add_interface,
+		   (rte_pcapng_t *self, uint16_t port, uint16_t link_type,
+		   const char *ifname, const char *ifdescr,
+		   const char *filter))
 {
 	struct pcapng_interface_block *hdr;
 	struct rte_eth_dev_info dev_info;
@@ -274,7 +273,7 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port,
 	hdr = (struct pcapng_interface_block *)buf;
 	*hdr = (struct pcapng_interface_block) {
 		.block_type = PCAPNG_INTERFACE_BLOCK,
-		.link_type = 1,		/* DLT_EN10MB - Ethernet */
+		.link_type = link_type,
 		.block_length = len,
 	};
 
@@ -319,6 +318,16 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port,
 	return write(self->outfd, buf, len);
 }
 
+RTE_VERSION_SYMBOL(26, int, rte_pcapng_add_interface,
+		   (rte_pcapng_t *self, uint16_t port,
+		   const char *ifname, const char *ifdescr,
+		   const char *filter))
+{
+	/* Call the new version with a default link_type (Ethernet) */
+	return rte_pcapng_add_interface(self, port, DLT_EN10MB,
+					ifname, ifdescr, filter);
+}
+
 /*
  * Write an Interface statistics block at the end of capture.
  */
diff --git a/lib/pcapng/rte_pcapng.h b/lib/pcapng/rte_pcapng.h
index 48f2b57564..1b3f9b9464 100644
--- a/lib/pcapng/rte_pcapng.h
+++ b/lib/pcapng/rte_pcapng.h
@@ -28,6 +28,9 @@
 extern "C" {
 #endif
 
+/* default link type for ethernet traffic */
+#define DLT_EN10MB 1
+
 /* Opaque handle used for functions in this library. */
 typedef struct rte_pcapng rte_pcapng_t;
 
@@ -71,6 +74,8 @@ rte_pcapng_close(rte_pcapng_t *self);
  *  The handle to the packet capture file
  * @param port
  *  The Ethernet port to report stats on.
+ * @param link_type
+ *  The link type (e.g., DLT_EN10MB).
  * @param ifname (optional)
  *  Interface name to record in the file.
  *  If not specified, name will be constructed from port
@@ -84,7 +89,7 @@ rte_pcapng_close(rte_pcapng_t *self);
  * must be added.
  */
 int
-rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port,
+rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 			 const char *ifname, const char *ifdescr,
 			 const char *filter);
 
-- 
2.27.0

Re: [PATCH v1] pcapng: allow any protocol link type for the interface block

[Stephen Hemminger]

On Wed, 27 Aug 2025 09:38:52 -0600
Schneide <schneide@qti.qualcomm.com> wrote:

> +use_function_versioning = true
> diff --git a/lib/pcapng/rte_pcapng.c b/lib/pcapng/rte_pcapng.c
> index 2a07b4c1f5..1ff8d14d08 100644
> --- a/lib/pcapng/rte_pcapng.c
> +++ b/lib/pcapng/rte_pcapng.c
> @@ -200,11 +200,10 @@ pcapng_section_block(rte_pcapng_t *self,
>  }
>  
>  /* Write an interface block for a DPDK port */
> -RTE_EXPORT_SYMBOL(rte_pcapng_add_interface)
> -int
> -rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port,
> -			 const char *ifname, const char *ifdescr,
> -			 const char *filter)
> +RTE_DEFAULT_SYMBOL(27, int, rte_pcapng_add_interface,
> +		   (rte_pcapng_t *self, uint16_t port, uint16_t link_type,
> +		   const char *ifname, const char *ifdescr,
> +		   const char *filter))
>  {
>  	struct pcapng_interface_block *hdr;
>  	struct rte_eth_dev_info dev_info;
> @@ -274,7 +273,7 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port,
>  	hdr = (struct pcapng_interface_block *)buf;
>  	*hdr = (struct pcapng_interface_block) {
>  		.block_type = PCAPNG_INTERFACE_BLOCK,
> -		.link_type = 1,		/* DLT_EN10MB - Ethernet */
> +		.link_type = link_type,
>  		.block_length = len,
>  	};
>  
> @@ -319,6 +318,16 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port,
>  	return write(self->outfd, buf, len);
>  }
>  
> +RTE_VERSION_SYMBOL(26, int, rte_pcapng_add_interface,
> +		   (rte_pcapng_t *self, uint16_t port,
> +		   const char *ifname, const char *ifdescr,
> +		   const char *filter))
> +{
> +	/* Call the new version with a default link_type (Ethernet) */
> +	return rte_pcapng_add_interface(self, port, DLT_EN10MB,
> +					ifname, ifdescr, filter);
> +}
> +

No symbol versioning needed for 25.11 release since it is major release.
The release note is enough.

Re: [PATCH v1] pcapng: allow any protocol link type for the interface block

[Stephen Hemminger]

On Wed, 27 Aug 2025 09:38:52 -0600
Schneide <schneide@qti.qualcomm.com> wrote:

> diff --git a/lib/pcapng/rte_pcapng.h b/lib/pcapng/rte_pcapng.h
> index 48f2b57564..1b3f9b9464 100644
> --- a/lib/pcapng/rte_pcapng.h
> +++ b/lib/pcapng/rte_pcapng.h
> @@ -28,6 +28,9 @@
>  extern "C" {
>  #endif
>  
> +/* default link type for ethernet traffic */
> +#define DLT_EN10MB 1
> +
>  

It would be good idea to guard this definition with #ifdef so
that if user includes pcap.h first, there is not conflict.

#ifndef DLT_EN10MB
#define DLT_EN10MB	1	/* Ethernet (10Mb) */
#endif