[PATCH v5 1/9] pcap: add pcap_iov()

[Laurent Vivier <lvivier@redhat.com>]

Introduce a new function pcap_iov() to capture packet desribed by an IO
vector.

Update pcap_frame() to manage iovcnt > 1.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---

Notes:
    v5:
      - add David's R-b
    
    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 */
-- 
@@ -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 */
-- 
2.42.0