On Thu, Feb 29, 2024 at 05:59:48PM +0100, Laurent Vivier wrote:
> Introduce a new function pcap_iov() to capture packet desribed by an IO
> vector.
> 
> Update pcap_frame() to manage iovcnt > 1.

Yikes.  I hadn't actually realised my version only worked for iovcnt
== 1.

> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
> 
> Notes:
>     v4:
>       - use pcap_frame()
>     
>     v3:
>       - update rationale
>       - update comment
>       - use strerror(errno)
>       - use size_t for io vector length
>     
>     v2:
>       - introduce pcap_header(), a common helper to write
>         packet header
>       - use writev() rather than write() in a loop
>       - add functions comment
> 
>  pcap.c | 26 ++++++++++++++++++++++----
>  pcap.h |  1 +
>  2 files changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/pcap.c b/pcap.c
> index a4057b5f9c6a..372f02045262 100644
> --- a/pcap.c
> +++ b/pcap.c
> @@ -32,6 +32,7 @@
>  #include "passt.h"
>  #include "log.h"
>  #include "pcap.h"
> +#include "iov.h"
>  
>  #define PCAP_VERSION_MINOR 4
>  
> @@ -78,7 +79,7 @@ struct pcap_pkthdr {
>  static void pcap_frame(const struct iovec *iov, size_t iovcnt,
>  		       size_t offset, const struct timeval *tv)
>  {
> -	size_t len = iov->iov_len - offset;
> +	size_t len = iov_size(iov, iovcnt) - offset;
>  	struct pcap_pkthdr h = {
>  		.tv_sec = tv->tv_sec,
>  		.tv_usec = tv->tv_usec,
> @@ -87,10 +88,8 @@ static void pcap_frame(const struct iovec *iov, size_t iovcnt,
>  	};
>  	struct iovec hiov = { &h, sizeof(h) };
>  
> -	(void)iovcnt;
> -
>  	if (write_remainder(pcap_fd, &hiov, 1, 0) < 0 ||
> -	    write_remainder(pcap_fd, iov, 1, offset) < 0) {
> +	    write_remainder(pcap_fd, iov, iovcnt, offset) < 0) {
>  		debug("Cannot log packet, length %zu: %s",
>  		      len, strerror(errno));
>  	}
> @@ -135,6 +134,25 @@ void pcap_multiple(const struct iovec *iov, size_t frame_parts, unsigned int n,
>  		pcap_frame(iov + i * frame_parts, frame_parts, offset, &tv);
>  }
>  
> +/*
> + * pcap_iov - Write packet data described by an I/O vector
> + *		to a pcap file descriptor.
> + *
> + * @iov:	Pointer to the array of struct iovec describing the I/O vector
> + *		containing packet data to write, including L2 header
> + * @iovcnt:	Number of buffers (@iov entries)
> + */
> +void pcap_iov(const struct iovec *iov, size_t iovcnt)
> +{
> +	struct timeval tv;
> +
> +	if (pcap_fd == -1)
> +		return;
> +
> +	gettimeofday(&tv, NULL);
> +	pcap_frame(iov, iovcnt, 0, &tv);
> +}
> +
>  /**
>   * pcap_init() - Initialise pcap file
>   * @c:		Execution context
> diff --git a/pcap.h b/pcap.h
> index 85fc58e57572..b1c4c909c109 100644
> --- a/pcap.h
> +++ b/pcap.h
> @@ -9,6 +9,7 @@
>  void pcap(const char *pkt, size_t len);
>  void pcap_multiple(const struct iovec *iov, size_t frame_parts, unsigned int n,
>  		   size_t offset);
> +void pcap_iov(const struct iovec *iov, size_t n);
>  void pcap_init(struct ctx *c);
>  
>  #endif /* PCAP_H */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson