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Date:      Sun, 1 Jul 2012 16:30:08 GMT
From:      Mikolaj Golub <trociny@freebsd.org>
To:        freebsd-bugs@FreeBSD.org
Subject:   Re: bin/151937: [patch] netstat(1) utility lack support of displaying rtt related counters of tcp sockets
Message-ID:  <201207011630.q61GU87S044475@freefall.freebsd.org>

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The following reply was made to PR bin/151937; it has been noted by GNATS.

From: Mikolaj Golub <trociny@freebsd.org>
To: Mykola Zubach <zuborg@example.com>, freebsd-net@FreeBSD.org
Cc: Robert Watson <rwatson@FreeBSD.org>, bug-followup@FreeBSD.org
Subject: Re: bin/151937: [patch] netstat(1) utility lack support of displaying rtt related counters of tcp sockets
Date: Sun, 01 Jul 2012 19:20:11 +0300

 --=-=-=
 
 Hi,
 
 Mykola, thank you for the report and the provided patch. Displaying rtt
 related counters per connection looks useful for me too.
 
 I am attaching the modified version of the patch to discuss (and commit if
 there are no objections or other suggestions).
 
 The differences from your version:
 
 1) '-T' option is already used. Also, I don't like very much adding yet
 another option, so I added the statistics to '-x' option. Or it can be added
 to '-T' statistics.
 
 2) As counter names I used names that are close to field names in the tcpcb
 structure.
 
 3) To get hz, instead of kern.clockrate, I use kern.hz sysctl (as it
 simplifies the code a little) and for !live case read it from the dump.
 
 4) The trick with printing to buf is used to pad the counters on the right, as
 it is with other counters.
 
 Also, it might be enough to display only srtt and rttvar statistics?
 
 -- 
 Mikolaj Golub
 
 --=-=-=
 Content-Type: text/x-patch
 Content-Disposition: attachment; filename=netstat.rtt.2.patch
 
 Index: usr.bin/netstat/inet.c
 ===================================================================
 --- usr.bin/netstat/inet.c	(revision 237835)
 +++ usr.bin/netstat/inet.c	(working copy)
 @@ -293,6 +293,28 @@ fail:
  #undef KREAD
  }
  
 +static const char *
 +humanize_rtt(int val, int scale)
 +{
 +	size_t len;
 +	static int hz;
 +	static char buf[16];
 +
 +	if (hz == 0) {
 +		hz = 1;
 +		if (live) {
 +			len = sizeof(hz);
 +			if (sysctlbyname("kern.hz", &hz, &len, NULL, 0) == -1)
 +				warn("sysctl: kern.hz");
 +		} else {
 +			kread(hz_addr, &hz, sizeof(hz));
 +		}
 +	}
 +	snprintf(buf, sizeof(buf), "%.3f", (float)val / (scale * hz));
 +
 +	return (buf);
 +}
 +
  /*
   * Print a summary of connections related to an Internet
   * protocol.  For TCP, also give state of connection.
 @@ -441,6 +463,8 @@ protopr(u_long off, const char *name, int af1, int
  				printf(" %7.7s %7.7s %7.7s %7.7s %7.7s %7.7s",
  				       "rexmt", "persist", "keep",
  				       "2msl", "delack", "rcvtime");
 +				printf(" %7.7s %7.7s %7.7s %9.9s",
 +				       "srtt", "rttvar", "rttlow", "rttupdate");
  			}
  			putchar('\n');
  			first = 0;
 @@ -548,6 +572,14 @@ protopr(u_long off, const char *name, int af1, int
  				    timer->tt_2msl / 1000, (timer->tt_2msl % 1000) / 10,
  				    timer->tt_delack / 1000, (timer->tt_delack % 1000) / 10,
  				    timer->t_rcvtime / 1000, (timer->t_rcvtime % 1000) / 10);
 +			if (tp != NULL) {
 +				printf(" %7s", humanize_rtt(tp->t_srtt,
 +				    TCP_RTT_SCALE));
 +				printf(" %7s", humanize_rtt(tp->t_rttvar,
 +				    TCP_RTTVAR_SCALE));
 +				printf(" %7s", humanize_rtt(tp->t_rttlow, 1));
 +				printf(" %9lu ", tp->t_rttupdated);
 +			}
  		}
  		if (istcp && !Lflag && !xflag && !Tflag) {
  			if (tp->t_state < 0 || tp->t_state >= TCP_NSTATES)
 Index: usr.bin/netstat/main.c
 ===================================================================
 --- usr.bin/netstat/main.c	(revision 237835)
 +++ usr.bin/netstat/main.c	(working copy)
 @@ -184,6 +184,8 @@ static struct nlist nl[] = {
  	{ .n_name = "_arpstat" },
  #define	N_UNP_SPHEAD	56
  	{ .n_name = "unp_sphead" },
 +#define	N_HZ		57
 +	{ .n_name = "_hz" },
  	{ .n_name = NULL },
  };
  
 @@ -358,6 +360,8 @@ int	unit;		/* unit number for above */
  int	af;		/* address family */
  int	live;		/* true if we are examining a live system */
  
 +u_long	hz_addr;	/* address of hz variable in kernel memory */
 +
  int
  main(int argc, char *argv[])
  {
 @@ -563,6 +567,7 @@ main(int argc, char *argv[])
  	 */
  #endif
  	kread(0, NULL, 0);
 +	hz_addr = nl[N_HZ].n_value;
  	if (iflag && !sflag) {
  		intpr(interval, nl[N_IFNET].n_value, NULL);
  		exit(0);
 Index: usr.bin/netstat/netstat.h
 ===================================================================
 --- usr.bin/netstat/netstat.h	(revision 237835)
 +++ usr.bin/netstat/netstat.h	(working copy)
 @@ -59,6 +59,8 @@ extern int	unit;	/* unit number for above */
  extern int	af;	/* address family */
  extern int	live;	/* true if we are examining a live system */
  
 +extern u_long	hz_addr;	/* address of hz variable in kernel memory */
 +
  int	kread(u_long addr, void *buf, size_t size);
  const char *plural(uintmax_t);
  const char *plurales(uintmax_t);
 
 --=-=-=--



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