When capturing packets into a PCAP file, DPDK currently uses
microseconds for the timestamps. But libpcap supports interpreting
tv_usec as nanoseconds depending on the file timestamp precision,
as of commit ba89e4a18e8b ("Make timestamps precision configurable").
To support this, use PCAP_TSTAMP_PRECISION_NANO when creating the
empty PCAP file as specified by PCAP_OPEN_DEAD(3PCAP) and implement
nanosecond timeval addition. This also ensures that the precision
reported by capinfos is nanoseconds (9).
Note that NSEC_PER_SEC is defined as 1000000000L instead of 1e9 since
the latter might be interpreted as floating point.
Signed-off-by: Vivien Didelot <vivien.dide...@gmail.com>
---
doc/guides/rel_notes/release_20_08.rst | 6 ++++++
drivers/net/pcap/rte_eth_pcap.c | 15 ++++++++++++---
2 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/doc/guides/rel_notes/release_20_08.rst
b/doc/guides/rel_notes/release_20_08.rst
index dee4ccbb5..7a67c960c 100644
--- a/doc/guides/rel_notes/release_20_08.rst
+++ b/doc/guides/rel_notes/release_20_08.rst
@@ -56,6 +56,12 @@ New Features
Also, make sure to start the actual text at the margin.
=========================================================
+* **Updated PCAP driver.**
+
+ Updated PCAP driver with new features and improvements, including:
+
+ * Support software Tx nanosecond timestamps precision.
+
* **Updated Mellanox mlx5 driver.**
Updated Mellanox mlx5 driver with new features and improvements, including:
diff --git a/drivers/net/pcap/rte_eth_pcap.c b/drivers/net/pcap/rte_eth_pcap.c
index b4c79d174..13a3d0ac7 100644
--- a/drivers/net/pcap/rte_eth_pcap.c
+++ b/drivers/net/pcap/rte_eth_pcap.c
@@ -287,6 +287,8 @@ eth_null_rx(void *queue __rte_unused,
return 0;
}
+#define NSEC_PER_SEC 1000000000L
+
static inline void
calculate_timestamp(struct timeval *ts) {
uint64_t cycles;
@@ -294,8 +296,14 @@ calculate_timestamp(struct timeval *ts) {
cycles = rte_get_timer_cycles() - start_cycles;
cur_time.tv_sec = cycles / hz;
- cur_time.tv_usec = (cycles % hz) * 1e6 / hz;
- timeradd(&start_time, &cur_time, ts);
+ cur_time.tv_usec = (cycles % hz) * NSEC_PER_SEC / hz;
+
+ ts->tv_sec = start_time.tv_sec + cur_time.tv_sec;
+ ts->tv_usec = start_time.tv_usec + cur_time.tv_usec;
+ if (ts->tv_usec >= NSEC_PER_SEC) {
+ ts->tv_usec -= NSEC_PER_SEC;
+ ts->tv_sec += 1;
+ }
}
/*
@@ -475,7 +483,8 @@ open_single_tx_pcap(const char *pcap_filename,
pcap_dumper_t **dumper)
* with pcap_dump_open(). We create big enough an Ethernet
* pcap holder.
*/
- tx_pcap = pcap_open_dead(DLT_EN10MB, RTE_ETH_PCAP_SNAPSHOT_LEN);
+ tx_pcap = pcap_open_dead_with_tstamp_precision(DLT_EN10MB,
+ RTE_ETH_PCAP_SNAPSHOT_LEN, PCAP_TSTAMP_PRECISION_NANO);
if (tx_pcap == NULL) {
PMD_LOG(ERR, "Couldn't create dead pcap");
return -1;
--
2.27.0
