forswan

forswan.py

#!/usr/bin/python
import time, sys

iface="eth0" if len(sys.argv) < 2 else sys.argv[1]
_prev_in = 0
_prev_out = 0
print "With interface: " + iface
with open("/proc/net/dev") as f: 
    while True:
        for row in f:
            [interface, lost] = row.split(":", 1) if ":" in row else [row, '']
            if (interface.strip() == iface):
                cnt=[int(x) for x in lost.split()]
                if len(cnt) < 9:
                    continue
                print "in: %s out: %s" % (
                            (cnt[1] - _prev_in),
                            (cnt[9] - _prev_out)
                        )
                _prev_in=cnt[1]
                _prev_out=cnt[9]
        f.seek(0)
        time.sleep(1)