Re: [PATCH v2] pcapng: allow any protocol link type for the interface block

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri,  6 Jun 2025 15:52:08 -0600
Schneide <schneide@qti.qualcomm.com> wrote:

> 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                     |  4 ++--
>  app/test/test_pcapng.c                 |  8 ++++----
>  doc/guides/rel_notes/release_25_07.rst |  5 ++++-
>  lib/graph/graph_pcap.c                 |  4 +++-
>  lib/pcapng/meson.build                 |  2 ++
>  lib/pcapng/rte_pcapng.c                | 21 +++++++++++++++------
>  lib/pcapng/rte_pcapng.h                |  4 +++-
>  8 files changed, 34 insertions(+), 15 deletions(-)
> 
> diff --git a/.mailmap b/.mailmap
> index 91e08f4a1f..a585124832 100644
> --- a/.mailmap
> +++ b/.mailmap
> @@ -390,6 +390,7 @@ 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..e0e2b26269 100644
> --- a/app/dumpcap/main.c
> +++ b/app/dumpcap/main.c
> @@ -800,8 +800,8 @@ 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_07.rst b/doc/guides/rel_notes/release_25_07.rst
> index 6b070801de..2396c7b014 100644
> --- a/doc/guides/rel_notes/release_25_07.rst
> +++ b/doc/guides/rel_notes/release_25_07.rst
> @@ -108,7 +108,10 @@ API Changes
>     This section is a comment. Do not overwrite or remove it.
>     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..13d86b7a18 100644
> --- a/lib/graph/graph_pcap.c
> +++ b/lib/graph/graph_pcap.c
> @@ -11,6 +11,8 @@
>  #include <rte_mbuf.h>
>  #include <rte_pcapng.h>
>  
> +#include <pcap/pcap.h>
> +
>  #include "rte_graph_worker.h"
>  
>  #include "graph_pcap_private.h"
> @@ -117,7 +119,7 @@ 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 cacbefdc50..f18af25983 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(26, 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(25, 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..9880d415c4 100644
> --- a/lib/pcapng/rte_pcapng.h
> +++ b/lib/pcapng/rte_pcapng.h
> @@ -71,6 +71,8 @@ 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 +86,7 @@ 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);
>  

Build is failing, DLT_EN10MB is not available in all configs.