svn commit: r303733 - head/contrib/libpcap

[Bruce Evans]

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