On Sat, 23 May 2020 13:21:29 -0400 Vivien Didelot <vivien.dide...@gmail.com> wrote:
> When capturing packets into a PCAP file, DPDK currently uses > microseconds for the timestamp. But libpcap supports interpreting > tv_usec as nanoseconds depending on the file timestamp precision. > > 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). > > Signed-off-by: Vivien Didelot <vivien.dide...@gmail.com> > --- > drivers/net/pcap/rte_eth_pcap.c | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/pcap/rte_eth_pcap.c b/drivers/net/pcap/rte_eth_pcap.c > index b4c79d174..68588c3d7 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 1e9 > + > 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; > + } Please no floating point math in the fast path of capturing packets!