#!/usr/bin/perl
#
# GPL V2 or greater
# work around Atheros ANI overly attenuating recieve chain with tendency to become stuck
# Joe Ayers AE6XE ae6xe@arrl.net 2015-10-29

# A receive chain may go deaf at noise prone sites and some neighbors may drop out.
# The wireless driver poorly tunes and treats these neighbors as noise in error.
# This is a workaround until root cause driver updates occur.

$now=`cat /proc/uptime | cut -f1 -d" "`;
chomp $now;

exit 0 unless $now > 120;

$iface = "wlan0" ; # wireless interface
$datfile = "/tmp/rssi.dat";
$logfile = "/tmp/rssi.log";

open(my $lfh, '>>', $logfile) or die "Could not open file $logfile $!";

sub getRSSI
{
  for (keys %rssi)
    {
        delete $rssi{$_};
    }

  open(FILE, "/usr/sbin/iw $iface station dump 2>&1 |") or die "/usr/sbin/iw failed $!";

  $neighborCount = 0;
  while($line = <FILE>)
  {
    if($line =~ /Station (\S+) \(on $iface\)/) { $mac = $1;}
    if($antnum and $line =~ /signal:[ \t]+[-\d]+[ \t]*\[([-\d]+),[ \t]*([-\d]+)/)
    {
      $H = $1;
      $V = $2;
    }

    if ((not $antnum) and $line =~ /signal:[ \t]+[-\d]+[ \t]*\[([-\d]+)\]/)
    {
      $H = $1;
    }
    if ($H)
    {
        if ($H < -95) { $rssi{$mac}{"Hrssi"}=-96 ; }
        else { $rssi{$mac}{"Hrssi"}=$H ; }
        undef $H;
        $neighborCount += 1;
    }
    if ($V)
    {
        if ($V < -95) { $rssi{$mac}{"Vrssi"}=-96 ; }
        else { $rssi{$mac}{"Vrssi"}=$V ; }
        undef $V;
    }
  }
}

$antnum=`iw list | grep "Configured Antennas: TX" | cut -f6 -d" "`;
chomp $antnum;
if ($antnum eq "0x1")
{
  $antnum=0;
}
else
{
  $antnum=1;  # more than one
}

if ( -e $datfile )
{
  open(FILE, "<$datfile") or die "Unable to read \"$datfile\"";

  while($line = <FILE>)
  {
    if ($antnum)
    {
      ($mac, $aveH, $aveV, $stdDevH, $stdDevV, $numS, $last) = split /\|/, $line;
      $rssiHist{$mac}{"aveV"} = $aveV;
      $rssiHist{$mac}{"sdV"} = $stdDevV;
    }
    else
    {
      ($mac, $aveH, $stdDevH, $numS, $last) = split /\|/, $line;
    }
    $rssiHist{$mac}{"aveH"} = $aveH;
    $rssiHist{$mac}{"sdH"} = $stdDevH;
    $rssiHist{$mac}{"num"} = $numS;
    chomp $last;
    $rssiHist{$mac}{"last"} = $last;
  }
  close FILE ;
}

$ofdm_level = `cat /sys/kernel/debug/ieee80211/phy0/ath9k/ani | grep "OFDM LEVEL" | cut -f2 -d: `;
$now=`cat /proc/uptime | cut -f1 -d" "`;
chomp $now;

getRSSI() ;

for (keys %rssi)
{
  if ( $rssiHist{$_} and $now - $rssiHist{$_}{"last"} < 3600 )
  {
    $hit = 0 ;
    $sdH3 = int(3 * $rssiHist{$_}{"sdH"} + .5);
    # is the RSSI attenuated and 3 standard deviations away?   Test is only 1 chain has dropped, not both.
    if   ($rssiHist{$_}{"aveH"} - $rssi{$_}{"Hrssi"}  > $sdH3) { $hit += 1; }
    if ( $antnum )
    {
      $sdV3 = int(3 * $rssiHist{$_}{"sdV"} + .5);
      if ($rssiHist{$_}{"aveV"} - $rssi{$_}{"Vrssi"}  >  $sdV3) { $hit += 1; }
    }

    if ($rssiHist{$_}{"num"} > 9 and $ofdm_level <= 2 and $hit == 1)
    { # Overly Attenuated Chain Suspected
      $datestring = localtime();
      if ($antnum)
      {
        print $lfh "$datestring: Attenuated Suspect $_ [$rssi{$_}{'Hrssi'},$rssi{$_}{'Vrssi'}] $rssiHist{$_}{'aveH'} ";
        print $lfh "$rssiHist{$_}{'aveV'} $rssiHist{$_}{'sdH'} $rssiHist{$_}{'sdV'}\n";
      }
      else
      {
        print $lfh "$datestring: Attenuated Suspect $_ [$rssi{$_}{'Hrssi'}] $rssiHist{$_}{'aveH'} $rssiHist{$_}{'sdH'}\n";
      }

      # find strongest signal to compare RSSI before/after reset
      if ( $amac )
      {
	if ($antnum)
        {
          if ($rssi{$amac}{"Hrssi"} < $rssi{$amac}{"Vrssi"} ) { $strong1 = "Vrssi" ;} else {$strong1 = "Hrssi";  }
          if ($rssi{$_}{"Hrssi"} < $rssi{$_}{"Vrssi"} ) { $strong2 = "Vrssi" ;} else {$strong2 = "Hrssi";  }
          if ($rssi{$amac}{$strong1} < $rssi{$_}{$strong2} ) { $amac = $_ ;}
        }
        else
        {
          if ($rssi{$amac}{"Hrssi"} < $rssi{$_}{"Hrssi"} ) { $amac = $_ ;}
        }
      }
      else { $amac = $_ ; }
      next ; # do not update statistics when suspected condition
    }

    # unpdate statistics
    $aveH = (($rssiHist{$_}{"aveH"}*$rssiHist{$_}{"num"})+$rssi{$_}{"Hrssi"}) / ($rssiHist{$_}{"num"} + 1 );
    $sdH = sqrt((($rssiHist{$_}{"num"}-1)*($rssiHist{$_}{"sdH"}**2) +
               (($rssi{$_}{"Hrssi"}-$aveH)*($rssi{$_}{"Hrssi"}-$rssiHist{$_}{"aveH"})))/$rssiHist{$_}{"num"});
    chomp $aveH;
    chomp $sdH;

    if ($antnum)
    {
      $aveV = (($rssiHist{$_}{"aveV"}*$rssiHist{$_}{"num"})+$rssi{$_}{"Vrssi"}) / ($rssiHist{$_}{"num"} + 1 );
      $sdV = sqrt((($rssiHist{$_}{"num"}-1)*($rssiHist{$_}{"sdV"}**2) +
               (($rssi{$_}{"Vrssi"}-$aveV)*($rssi{$_}{"Vrssi"}-$rssiHist{$_}{"aveV"})))/$rssiHist{$_}{"num"});
      chomp $aveV;
      chomp $sdV;
    }

    $rssiHist{$_}{"aveH"} = $aveH;
    $rssiHist{$_}{"sdH"} =  $sdH;
    $rssiHist{$_}{"last"} = $now;
    if ($rssiHist{$_}{"num"} < 60 ) 
    {
      # keep statistics to 60 sample (minute) moving window
      $rssiHist{$_}{"num"} += 1;
    }
    if ($antnum)
    {
      $rssiHist{$_}{"aveV"} = $aveV;
      $rssiHist{$_}{"sdV"} =  $sdV;
    }
  }
  else
  {  # new neigbor or data too old--restart history
    $rssiHist{$_}{"aveH"} = $rssi{$_}{"Hrssi"};
    $rssiHist{$_}{"sdH"} = 0;
    $rssiHist{$_}{"num"} = 1;
    $rssiHist{$_}{"last"} = $now;
    if ($antnum)
    {
      $rssiHist{$_}{"aveV"} = $rssi{$_}{"Vrssi"};
      $rssiHist{$_}{"sdV"} = 0;
    }
  }
}

if ($amac or not $neighborCount)
{
  $chnum = `uci get wireless.radio0.channel`;
  $chnum += 1;
  if ($chnum == 8 or $chnum == 12 or $chnum == 100 or $chnum == 185) { $chnum -= 2; }
  if ($chnum == 0) { $chnum = 1; }
  $freq = `iw list | grep "\\\[$chnum\\\]" | head -1`;
  $freq =~ /([\d]+)[ \t]+MHz[ \t]+/;
  $freq = $1;

  if ($amac)
  {
    $datestring = localtime();
    if ($antnum) {print $lfh "$datestring: before $amac [ $rssi{$amac}{'Hrssi'}, $rssi{$amac}{'Vrssi'} ]\n";}
    else         {print $lfh "$datestring: before $amac [ $rssi{$amac}{'Hrssi'}]\n";}
  }

  system("/usr/sbin/iw $iface scan freq $freq passive > /dev/null");

  if ($amac)
  {
    sleep 5;

    $beforeH = $rssi{$amac}{"Hrssi"};
    if ($antnum) { $beforeV = $rssi{$amac}{"Vrssi"}; }

    getRSSI() ;
    $datestring = localtime();
    if ($antnum) {print $lfh "$datestring: after  $amac [ $rssi{$amac}{'Hrssi'}, $rssi{$amac}{'Vrssi'} ]\n";}
    else         {print $lfh "$datestring: after  $amac [ $rssi{$amac}{'Hrssi'}]\n";}

    $falpos = 0;
    if ($antnum)
    {
      if  (abs ( $beforeH - $rssi{$amac}{"Hrssi"} ) <= 2 and 
           abs ( $beforeV - $rssi{$amac}{"Vrssi"} ) <= 2 ) { $falpos = 1; }
    }
    elsif (abs ( $beforeH - $rssi{$amac}{"Hrssi"} ) <= 2 ) { $falpos = 1; }

    if ( $falpos )
    {
      # if a false-positive (within 2dB change after a reset), then add data point to statistics
      $aveH = (($rssiHist{$amac}{"aveH"}*$rssiHist{$amac}{"num"})+ $beforeH ) 
                                                / ($rssiHist{$amac}{"num"} + 1 );
      $sdH = sqrt((($rssiHist{$amac}{"num"}-1)*($rssiHist{$amac}{"sdH"}**2) +
                 (($beforeH-$aveH)*($beforeH-$rssiHist{$amac}{"aveH"})))
                                           /$rssiHist{$amac}{"num"});
      chomp $aveH;
      chomp $sdH;
      $rssiHist{$amac}{"aveH"} = $aveH;
      $rssiHist{$amac}{"sdH"} =  $sdH;
  
      if ($antnum)
      {
        $aveV = (($rssiHist{$amac}{"aveV"}*$rssiHist{$amac}{"num"})+ $beforeV ) / 
                                                    ($rssiHist{$amac}{"num"} + 1 );
        $sdV = sqrt((($rssiHist{$amac}{"num"}-1)*($rssiHist{$amac}{"sdV"}**2) +
                             (($beforeV-$aveV)*($beforeV-$rssiHist{$amac}{"aveV"}))) /
                                                        $rssiHist{$amac}{"num"});
        chomp $aveV;
        chomp $sdV;
        $rssiHist{$amac}{"aveV"} = $aveV;
        $rssiHist{$amac}{"sdV"} =  $sdV;
      }

      if ($rssiHist{$amac}{"num"} < 60 ) 
      {
        # keep statistics to 60 sample (minute) moving window
        $rssiHist{$amac}{"num"} += 1;
      }
      $rssiHist{$amac}{"last"} = $now + 5 ;
  
      $datestring = localtime();
      print $lfh "$datestring: $amac Possible valid data point, adding to statistics.\n";
    }
  }
}

close $lfh;

open($dfh, ">$datfile") or die "Unable to create \"$datfile\" $!";
for (keys %rssiHist)
{
  if ($antnum)
  {
    print $dfh "$_|$rssiHist{$_}{'aveH'}|$rssiHist{$_}{'aveV'}|$rssiHist{$_}{'sdH'}|";
    print $dfh "$rssiHist{$_}{'sdV'}|$rssiHist{$_}{'num'}|$rssiHist{$_}{'last'}\n";
  }
  else
  {
    print $dfh "$_|$rssiHist{$_}{'aveH'}|$rssiHist{$_}{'sdH'}|$rssiHist{$_}{'num'}|$rssiHist{$_}{'last'}\n";
  }
}

close $dfh;

# when logfile gets 1k over $MAXSIZE, then chop down
$MAXSIZE = 2**14;
exit 0 unless -s $logfile > $MAXSIZE + 1024;
@ARGV = $logfile;
undef $/;
$^I = "";
while (<>) 
{
  substr($_, 0, $MAXSIZE - length) = "";
  s/.*\n//;
  print;
}