RE: [PATCH 2/4] dumpcap: allow multiple invocations

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Thursday, 21 September 2023 06.24
> 
> If dumpcap is run twice with each instance pointing a different
> interface, it would fail because of overlap in ring a pool names.
> Fix by putting process id in the name.
> 
> Fixes: cbb44143be74 ("app/dumpcap: add new packet capture application")
> Reported-by: Isaac Boukris <iboukris@gmail.com>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>  app/dumpcap/main.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/app/dumpcap/main.c b/app/dumpcap/main.c
> index 64294bbfb3e6..37754fd06f4f 100644
> --- a/app/dumpcap/main.c
> +++ b/app/dumpcap/main.c
> @@ -44,7 +44,6 @@
>  #include <pcap/pcap.h>
>  #include <pcap/bpf.h>
> 
> -#define RING_NAME "capture-ring"
>  #define MONITOR_INTERVAL  (500 * 1000)
>  #define MBUF_POOL_CACHE_SIZE 32
>  #define BURST_SIZE 32
> @@ -647,6 +646,7 @@ static void dpdk_init(void)
>  static struct rte_ring *create_ring(void)
>  {
>  	struct rte_ring *ring;
> +	char ring_name[RTE_RING_NAMESIZE];
>  	size_t size, log2;
> 
>  	/* Find next power of 2 >= size. */
> @@ -660,28 +660,28 @@ static struct rte_ring *create_ring(void)
>  		ring_size = size;
>  	}
> 
> -	ring = rte_ring_lookup(RING_NAME);
> -	if (ring == NULL) {
> -		ring = rte_ring_create(RING_NAME, ring_size,
> -					rte_socket_id(), 0);
> -		if (ring == NULL)
> -			rte_exit(EXIT_FAILURE, "Could not create ring :%s\n",
> -				 rte_strerror(rte_errno));
> -	}
> +	/* Want one ring per invocation of program */
> +	snprintf(ring_name, sizeof(ring_name),
> +		 "dumpcap-%u", getpid());

I'm not sure getpid() is available on Windows. How about:

#ifdef _WIN32
#include <processthreadsapi.h> // With the headers, not here.
"dumpcap-%lu", GetCurrentProcessId());
#else
"dumpcap-%u", getpid());
#endif

> +
> +	ring = rte_ring_create(ring_name, ring_size,
> +			       rte_socket_id(), 0);
> +	if (ring == NULL)
> +		rte_exit(EXIT_FAILURE, "Could not create ring :%s\n",
> +			 rte_strerror(rte_errno));
> +
>  	return ring;
>  }
> 
>  static struct rte_mempool *create_mempool(void)
>  {
>  	const struct interface *intf;
> -	static const char pool_name[] = "capture_mbufs";
> +	char pool_name[RTE_MEMPOOL_NAMESIZE];
>  	size_t num_mbufs = 2 * ring_size;
>  	struct rte_mempool *mp;
>  	uint32_t data_size = 128;
> 
> -	mp = rte_mempool_lookup(pool_name);
> -	if (mp)
> -		return mp;
> +	snprintf(pool_name, sizeof(pool_name), "capture_%u", getpid());

Same regarding getpid().

> 
>  	/* Common pool so size mbuf for biggest snap length */
>  	TAILQ_FOREACH(intf, &interfaces, next) {
> @@ -826,7 +826,7 @@ static void enable_pdump(struct rte_ring *r, struct
> rte_mempool *mp)
>  			rte_exit(EXIT_FAILURE,
>  				"Packet dump enable on %u:%s failed %s\n",
>  				intf->port, intf->name,
> -				rte_strerror(-ret));
> +				rte_strerror(rte_errno));
>  		}
> 
>  		if (intf->opts.promisc_mode) {
> --
> 2.39.2