== Getting live network bandwidth numbers on Solaris

After I wrote [[netvolmon for Linux ../linux/SeeingNetworkBandwidth]],
I started getting curious about how much bandwidth our current Solaris
NFS servers were using. Unfortunately, Solaris's version of _ifconfig_
does not report byte counts; fortunately, the kernel does keep this
information and you can dig it out with _kstat_ (information courtesy
of [[here http://www.brendangregg.com/Perf/network.html]], which has a
bunch of more sophisticated programs to report on this stuff).

The magic _kstat_ incantation is '((kstat -p "*:*:<DEV>:*bytes64"))',
which gets you the obytes64 and rbytes64 counters for the device; this
works on at least Solaris 8 and Solaris 10. (In this Solaris does Linux
one better, since a 32-bit Linux machines use 32-bit network counters
and on a saturated gigabit link they can roll over in under 20 seconds.)

Armed with this we can write the obvious Solaris version of _netvolmon_:

 #!/bin/sh
 # usage: netvolmon DEV [INTERVAL]
 DEV=$1
 IVAL=${2:-5}
 
 getrxtx() {
     kstat -p "*:*:$1:*bytes64" |
         awk '{print $2}'
 }
 
 rxtx=`getrxtx $DEV`
 while sleep $IVAL; do
     nrxtx=`getrxtx $DEV`
     (echo $IVAL $rxtx $nrxtx) |
     awk 'BEGIN {
           msg = "%6.2f MB/s RX %6.2f MB/s TX\n"}
          {rxd = ($4 - $2) / (1024*1024*$1);
           txd = ($5 - $3) / (1024*1024*$1);
           printf msg, rxd, txd}'
     rxtx="$nrxtx"
 done

Vaguely to my surprise, it turns out that Solaris 8 awk doesn't allow
you to split _printf_ (and presumably _print_) statements over multiple
lines. The Solaris shell is backwards and doesn't support the POSIX
shell _$(...)_ syntax, even in Solaris 10, so this version uses the less
pleasant backquote syntax.

(This can easily be extended to report packets per second as well; the
device counters you want are 'opackets64' and 'rpackets64'. I didn't put
it in this version for a petty reason, namely that it would make this
entry too wide, but you can get the full versions for both Solaris and
Linux [[here </~cks/programs/sysadmin/>]].)