Re: [PATCH v4 1/8] pcap: add pcap_iov()

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(a)redhat.com> 
Reviewed-by: David Gibson <david(a)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