Date: Thu, 4 Aug 2016 13:40:38 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Jung-uk Kim <jkim@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r303733 - head/contrib/libpcap Message-ID: <20160804124849.Y1045@besplex.bde.org> In-Reply-To: <201608032008.u73K8dWe047330@repo.freebsd.org> References: <201608032008.u73K8dWe047330@repo.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, 3 Aug 2016, Jung-uk Kim wrote:
> Log:
> Support nanosecond time stamps for pcap_dispatch(3) and pcap_loop(3).
>
> Modified:
> head/contrib/libpcap/pcap-bpf.c
>
> Modified: head/contrib/libpcap/pcap-bpf.c
> ==============================================================================
> --- head/contrib/libpcap/pcap-bpf.c Wed Aug 3 19:23:22 2016 (r303732)
> +++ head/contrib/libpcap/pcap-bpf.c Wed Aug 3 20:08:39 2016 (r303733)
> @@ -1008,7 +1028,25 @@ pcap_read_bpf(pcap_t *p, int cnt, pcap_h
> if (pb->filtering_in_kernel ||
> bpf_filter(p->fcode.bf_insns, datap, bhp->bh_datalen, caplen)) {
> struct pcap_pkthdr pkthdr;
> +#ifdef BIOCSTSTAMP
> + struct bintime bt;
> +
> + bt.sec = bhp->bh_tstamp.bt_sec;
> + bt.frac = bhp->bh_tstamp.bt_frac;
The names are very confusing since bt_sec and bt_frac are only misnamed as
sec and frac in struct bintime.
> + if (p->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO) {
> + struct timespec ts;
> +
> + bintime2timespec(&bt, &ts);
> + pkthdr.ts.tv_sec = ts.tv_sec;
> + pkthdr.ts.tv_usec = ts.tv_nsec;
And this abuses tv_usec to hold nanoseconds.
Old code is even more confusing, and at least partly wrong.
X contrib/libpcap/pcap-bpf.c: pkthdr.ts.tv_usec = bhp->bh_tstamp.tv_usec/1000;
This is to convert for tv_usec actually being tv_nsec on AIX. If the above
works with no conversion, then it might work for AIX too.
X sys/net/bpf.c: struct timeval32 bh_tstamp; /* time stamp */
Banal comment. The complexities are from what sort of timestamp this is.
It is obviously a timestamp.
This bh_tstamp is in struct bpf_hdr32 for the !BURN_BRIDGES case. There
is also struct timeval bh_timestamp in struct bpf_hdr. This header is
bogusly marked Obsolete.
X sys/net/bpf.c: hdr32_old.bh_tstamp.tv_usec = ts.bt_frac;
This is in the !BURN_BRIDGES && COMPAT_FREEBSD32 case. Since struct timeval32
always has a 32-bit tv_usec, this assignment discards the most significant
bits in bt_frac but keeps the noise.
X sys/net/bpf.c: hdr_old.bh_tstamp.tv_usec = ts.bt_frac;
This is in the !BURN_BRIDGES && !COMPAT_FREEBSD32 case. Since tv_sec in a
normal timetamp is bogusly long, this accidentally preserves all of the bits
in bt_frac on 64-bit arches. On 32-bit arches, it loses the signal as for
the COMPAT_FREEBSD32 case.
Bruce
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20160804124849.Y1045>