On Wed, 3 Jun 2020 18:50:51 +0100 Ferruh Yigit <ferruh.yi...@intel.com> wrote:
> On 5/23/2020 6:21 PM, Vivien Didelot 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). > > Overall good idea and patch looks good. > > Only concern is change in the libpcap dependency. Do you know which libpcap > version supports 'PCAP_TSTAMP_PRECISION_NANO'? > If a user of pcap PMD updates to latest DPDK and the environment doesn't have > new version of the libpcap, this change will require an environment update and > this may or may not be easy to do. That is why not sure if the updates require > dependency change should wait for the LTS or not. > > Another things is the backward compatibility, as far as I understand the pcap > file recorded with nanosecond precision can be read and parsed without problem > by old application that doesn't know the nanosecond precision, but can you > please confirm this? We should do pcapng instead of doing the pcap with nano timestamp. My impression is that libpcap is a dormant project at this point, and the finer grain timestamp is a hack that is only in some verisions. That was one of the reasons pcapng started.
