[PATCH iproute2] ip: support of usec rtt in tcp_metrics

[PATCH iproute2] ip: support of usec rtt in tcp_metrics

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Starting from linux-3.15, kernel supports new tcp metric attributes :
TCP_METRIC_RTT_US & TCP_METRIC_RTTVAR_US

Update ip command to detect their use.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 ip/tcp_metrics.c |   31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/ip/tcp_metrics.c b/ip/tcp_metrics.c
index e0f0344..bbbb4cc 100644
--- a/ip/tcp_metrics.c
+++ b/ip/tcp_metrics.c
@@ -216,6 +216,7 @@ static int process_msg(const struct sockaddr_nl *who, struct nlmsghdr *n,
 	a = attrs[TCP_METRICS_ATTR_VALS];
 	if (a) {
 		struct rtattr *m[TCP_METRIC_MAX + 1 + 1];
+		unsigned long rtt = 0, rttvar = 0;
 
 		parse_rtattr_nested(m, TCP_METRIC_MAX + 1, a);
 
@@ -225,18 +226,30 @@ static int process_msg(const struct sockaddr_nl *who, struct nlmsghdr *n,
 			a = m[i + 1];
 			if (!a)
 				continue;
-			if (metric_name[i])
-				fprintf(fp, " %s ", metric_name[i]);
-			else
-				fprintf(fp, " metric_%d ", i);
-
+			if (i != TCP_METRIC_RTT &&
+			    i != TCP_METRIC_RTT_US &&
+			    i != TCP_METRIC_RTTVAR &&
+			    i != TCP_METRIC_RTTVAR_US) {
+				if (metric_name[i])
+					fprintf(fp, " %s ", metric_name[i]);
+				else
+					fprintf(fp, " metric_%d ", i);
+			}
 			val = rta_getattr_u32(a);
 			switch (i) {
 			case TCP_METRIC_RTT:
-				fprintf(fp, "%luus", (val * 1000UL) >> 3);
+				if (!rtt)
+					rtt = (val * 1000UL) >> 3;
 				break;
 			case TCP_METRIC_RTTVAR:
-				fprintf(fp, "%luus", (val * 1000UL) >> 2);
+				if (!rttvar)
+					rttvar = (val * 1000UL) >> 2;
+				break;
+			case TCP_METRIC_RTT_US:
+				rtt = val >> 3;
+				break;
+			case TCP_METRIC_RTTVAR_US:
+				rttvar = val >> 2;
 				break;
 			case TCP_METRIC_SSTHRESH:
 			case TCP_METRIC_CWND:
@@ -246,6 +259,10 @@ static int process_msg(const struct sockaddr_nl *who, struct nlmsghdr *n,
 				break;
 			}
 		}
+		if (rtt)
+			fprintf(fp, " rtt %luus", rtt);
+		if (rttvar)
+			fprintf(fp, " rttvar %luus", rttvar);
 	}
 
 	a = attrs[TCP_METRICS_ATTR_FOPEN_MSS];

Re: [PATCH iproute2] ip: support of usec rtt in tcp_metrics

[Stephen Hemminger]

On Fri, 05 Sep 2014 16:54:04 -0700
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> +			if (i != TCP_METRIC_RTT &&
> +			    i != TCP_METRIC_RTT_US &&
> +			    i != TCP_METRIC_RTTVAR &&
> +			    i != TCP_METRIC_RTTVAR_US) {
> +				if (metric_name[i])
> +					fprintf(fp, " %s ", metric_name[i]);
> +				else
> +					fprintf(fp, " metric_%d ", i);

Why not put new metrics in metric_name array? and make the check something like:

			if (i < ARRAY_SIZE(metric_name) && metric_name[i])
				fprintf(fp, " %s ", metric_name[i]);
			else
				fprintf(fp, " metric_%d ", i)

This makes it future proof, and gets rid of the silly test.

Re: [PATCH iproute2] ip: support of usec rtt in tcp_metrics

[Eric Dumazet]

On Fri, 2014-09-05 at 17:02 -0700, Stephen Hemminger wrote:
> On Fri, 05 Sep 2014 16:54:04 -0700
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> 
> > +			if (i != TCP_METRIC_RTT &&
> > +			    i != TCP_METRIC_RTT_US &&
> > +			    i != TCP_METRIC_RTTVAR &&
> > +			    i != TCP_METRIC_RTTVAR_US) {
> > +				if (metric_name[i])
> > +					fprintf(fp, " %s ", metric_name[i]);
> > +				else
> > +					fprintf(fp, " metric_%d ", i);
> 
> Why not put new metrics in metric_name array? and make the check something like:
> 
> 			if (i < ARRAY_SIZE(metric_name) && metric_name[i])
> 				fprintf(fp, " %s ", metric_name[i]);
> 			else
> 				fprintf(fp, " metric_%d ", i)
> 
> This makes it future proof, and gets rid of the silly test.


Because for compatibility reasons, kernel gives all values,
we want to output one of them, the most accurate one.

Re: [PATCH iproute2] ip: support of usec rtt in tcp_metrics

[Stephen Hemminger]

On Fri, 05 Sep 2014 16:54:04 -0700
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> From: Eric Dumazet <edumazet@google.com>
> 
> Starting from linux-3.15, kernel supports new tcp metric attributes :
> TCP_METRIC_RTT_US & TCP_METRIC_RTTVAR_US
> 
> Update ip command to detect their use.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied thanks