[PATCH] pcap: Use clock_gettime() instead of gettimeofday() - dev

12 Mar 2024

POSIX.1-2008 declared gettimeofday() as obsolete, but I'm a dinosaur.

Usually, C libraries translate that to the clock_gettime() system
call anyway, but this doesn't happen in Jon's environment, and,
there, seccomp happily kills pasta(1) when started with --pcap,
because we didn't add gettimeofday() to our seccomp profiles.

Use clock_gettime() instead.

Reported-by: Jon Maloy &lt;jmaloy(a)redhat.com&gt;
Signed-off-by: Stefano Brivio &lt;sbrivio(a)redhat.com&gt;
---
 pcap.c | 26 +++++++++++++-------------
 util.h |  1 +
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/pcap.c b/pcap.c
index a0f01ad..45bbfcd 100644
--- a/pcap.c
+++ b/pcap.c
@@ -72,17 +72,17 @@ struct pcap_pkthdr {
  * @iov:	IO vector containing frame (with L2 headers and tap headers)
  * @iovcnt:	Number of buffers (@iov entries) in frame
  * @offset:	Byte offset of the L2 headers within @iov
- * @tv:		Timestamp
+ * @now:	Timestamp
  *
  * Returns: 0 on success, -errno on error writing to the file
  */
 static void pcap_frame(const struct iovec *iov, size_t iovcnt,
-		       size_t offset, const struct timeval *tv)
+		       size_t offset, const struct timespec *now)
 {
 	size_t len = iov_size(iov, iovcnt) - offset;
 	struct pcap_pkthdr h = {
-		.tv_sec = tv->tv_sec,
-		.tv_usec = tv->tv_usec,
+		.tv_sec = now->tv_sec,
+		.tv_usec = DIV_ROUND_CLOSEST(now->tv_nsec, 1000),
 		.caplen = len,
 		.len = len
 	};
@@ -103,13 +103,13 @@ static void pcap_frame(const struct iovec *iov, size_t iovcnt,
 void pcap(const char *pkt, size_t len)
 {
 	struct iovec iov = { (char *)pkt, len };
-	struct timeval tv;
+	struct timespec now;
 
 	if (pcap_fd == -1)
 		return;
 
-	gettimeofday(&tv, NULL);
-	pcap_frame(&iov, 1, 0, &tv);
+	clock_gettime(CLOCK_REALTIME, &now);
+	pcap_frame(&iov, 1, 0, &now);
 }
 
 /**
@@ -122,16 +122,16 @@ 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)
 {
-	struct timeval tv;
+	struct timespec now;
 	unsigned int i;
 
 	if (pcap_fd == -1)
 		return;
 
-	gettimeofday(&tv, NULL);
+	clock_gettime(CLOCK_REALTIME, &now);
 
 	for (i = 0; i < n; i++)
-		pcap_frame(iov + i * frame_parts, frame_parts, offset, &tv);
+		pcap_frame(iov + i * frame_parts, frame_parts, offset, &now);
 }
 
 /*
@@ -145,13 +145,13 @@ void pcap_multiple(const struct iovec *iov, size_t frame_parts,
unsigned int n,
 /* cppcheck-suppress unusedFunction */
 void pcap_iov(const struct iovec *iov, size_t iovcnt)
 {
-	struct timeval tv;
+	struct timespec now;
 
 	if (pcap_fd == -1)
 		return;
 
-	gettimeofday(&tv, NULL);
-	pcap_frame(iov, iovcnt, 0, &tv);
+	clock_gettime(CLOCK_REALTIME, &now);
+	pcap_frame(iov, iovcnt, 0, &now);
 }
 
 /**
diff --git a/util.h b/util.h
index 25e54a7..48f3560 100644
--- a/util.h
+++ b/util.h
@@ -40,6 +40,7 @@
 #endif
 
 #define DIV_ROUND_UP(n, d)	(((n) + (d) - 1) / (d))
+#define DIV_ROUND_CLOSEST(n, d)	(((n) + (d) / 2) / (d))
 #define ROUND_DOWN(x, y)	((x) & ~((y) - 1))
 #define ROUND_UP(x, y)		(((x) + (y) - 1) & ~((y) - 1))
 
-- 
2.39.2


    