snmp_session.pm

主要用于监控网络流量并动态产生可视化结果

# -*- mode: Perl -*-
######################################################################
### SNMP Request/Response Handling
######################################################################
### The abstract class SNMP_Session defines objects that can be used
### to communicate with SNMP entities.  It has methods to send
### requests to and receive responses from an agent.
###
### Currently it has one subclass, SNMPv1_Session, which implements
### the SNMPv1 protocol.
######################################################################
### Created by:  Simon Leinen  <[e-mail]>
###
### Contributions and fixes by:
###
### Matthew Trunnell <[e-mail]>
### Tobias Oetiker <[e-mail]>
### Heine Peters <[e-mail]>
### Daniel L. Needles <[e-mail]>
### Mike Mitchell <[e-mail]>
### Clinton Wong <[e-mail]>
### Alan Nichols <[e-mail]>
### Mike McCauley <[e-mail]>
######################################################################

package SNMP_Session;		

require 5.002;

use strict qw(vars subs);	# cannot use strict subs here
				# because of the way we use
				# generated file handles
use Exporter;
use vars qw(@ISA $VERSION @EXPORT $errmsg $suppress_warnings);
use Socket;
use BER;

sub map_table ($$$);
sub map_table_4 ($$$$);
sub map_table_start_end ($$$$$$);
sub index_compare ($$);
sub oid_diff ($$);

$VERSION = '0.71';

@ISA = qw(Exporter);

@EXPORT = qw(errmsg suppress_warnings index_compare oid_diff);

my $default_debug = 0;

### Default initial timeout (in seconds) waiting for a response PDU
### after a request is sent.  Note that when a request is retried, the
### timeout is increased by BACKOFF (see below).
###
my $default_timeout = 2.0;

### Default number of retries for each SNMP request.  If no response
### is received after TIMEOUT seconds, the request is resent and a new
### response awaited with a longer timeout (see the documentation on
### BACKOFF below).
###
my $default_retries = 5;

### Default backoff factor for SNMP_Session objects.  This factor is
### used to increase the TIMEOUT every time an SNMP request is
### retried.
###
my $default_backoff = 1.0;

### Default value for maxRepetitions.  This specifies how many table
### rows are requested in getBulk requests.  Used when walking tables
### using getBulk (only available in SNMPv2(c) and later).  If this is
### too small, then a table walk will need unnecessarily many
### request/response exchanges.  If it is too big, the agent may
### compute many variables after the end of the table.  It is
### recommended to set this explicitly for each table walk by using
### map_table_4().
###
my $default_max_repetitions = 12;

$SNMP_Session::errmsg = '';
$SNMP_Session::suppress_warnings = 2;

sub get_request      { 0 | context_flag };
sub getnext_request  { 1 | context_flag };
sub get_response     { 2 | context_flag };
sub set_request      { 3 | context_flag };
sub trap_request     { 4 | context_flag };
sub getbulk_request  { 5 | context_flag };
sub inform_request   { 6 | context_flag };
sub trap2_request    { 7 | context_flag };

sub standard_udp_port { 161 };

sub open
{
    return SNMPv1_Session::open (@_);
}

sub timeout { $_[0]->{timeout} }
sub retries { $_[0]->{retries} }
sub backoff { $_[0]->{backoff} }
sub set_timeout {
    my ($session, $timeout) = @_;
    die "timeout ($timeout) must be a positive number" unless $timeout > 0.0;
    $session->{'timeout'} = $timeout;
}
sub set_retries {
    my ($session, $retries) = @_;
    die "retries ($retries) must be a non-negative integer"
	unless $retries == int ($retries) && $retries >= 0;
    $session->{'retries'} = $retries; 
}
sub set_backoff {
    my ($session, $backoff) = @_;
    die "backoff ($backoff) must be a number >= 1.0"
	unless $backoff == int ($backoff) && $backoff >= 1.0;
    $session->{'backoff'} = $backoff; 
}

sub encode_request_3 ($$$@)
{
    my($this, $reqtype, $encoded_oids_or_pairs, $i1, $i2) = @_;
    my($request);
    local($_);

    ++$this->{request_id};
    foreach $_ (@{$encoded_oids_or_pairs}) {
      if (ref ($_) eq 'ARRAY') {
	$_ = &encode_sequence ($_->[0], $_->[1])
	  || return $this->ber_error ("encoding pair");
      } else {
	$_ = &encode_sequence ($_, encode_null())
	  || return $this->ber_error ("encoding value/null pair");
      }
    }
    $request = encode_tagged_sequence
	($reqtype,
	 encode_int ($this->{request_id}),
	 defined $i1 ? encode_int ($i1) : encode_int_0,
	 defined $i2 ? encode_int ($i2) : encode_int_0,
	 encode_sequence (@{$encoded_oids_or_pairs}))
	  || return $this->ber_error ("encoding request PDU");
    return $this->wrap_request ($request);
}

sub encode_get_request
{
    my($this, @oids) = @_;
    return encode_request_3 ($this, get_request, \@oids);
}

sub encode_getnext_request
{
    my($this, @oids) = @_;
    return encode_request_3 ($this, getnext_request, \@oids);
}

sub encode_getbulk_request
{
    my($this, $non_repeaters, $max_repetitions, @oids) = @_;
    return encode_request_3 ($this, getbulk_request, \@oids,
			     $non_repeaters, $max_repetitions);
}

sub encode_set_request
{
    my($this, @encoded_pairs) = @_;
    return encode_request_3 ($this, set_request, \@encoded_pairs);
}

sub encode_trap_request ($$$$$$@)
{
    my($this, $ent, $agent, $gen, $spec, $dt, @pairs) = @_;
    my($request);
    local($_);

    foreach $_ (@pairs) {
      if (ref ($_) eq 'ARRAY') {
	$_ = &encode_sequence ($_->[0], $_->[1])
	  || return $this->ber_error ("encoding pair");
      } else {
	$_ = &encode_sequence ($_, encode_null())
	  || return $this->ber_error ("encoding value/null pair");
      }
    }
    $request = encode_tagged_sequence
	(trap_request, $ent, $agent, $gen, $spec, $dt, encode_sequence (@pairs))
	  || return $this->ber_error ("encoding trap PDU");
    return $this->wrap_request ($request);
}

sub decode_get_response
{
    my($this, $response) = @_;
    my @rest;
    @{$this->{'unwrapped'}};
}

sub decode_trap_request ($$) {
    my ($this, $trap) = @_;
    my ($snmp_version, $community, $ent, $agent, $gen, $spec, $dt,
	$bindings);
    ($snmp_version, $community, $ent, $agent, $gen, $spec, $dt, $bindings)
	= decode_by_template ($trap, "%{%i%s%*{%O%A%i%i%u%{%@",
			      SNMP_Session::trap_request
			      );
    return undef
	unless $snmp_version == $this->snmp_version ();
    if (!defined $ent) {
	warn "BER error decoding trap:\n  ".$BER::errmsg."\n";
    }
    return ($community, $ent, $agent, $gen, $spec, $dt, $bindings);
}

sub wait_for_response
{
    my($this) = shift;
    my($timeout) = shift || 10.0;
    my($rin,$win,$ein) = ('','','');
    my($rout,$wout,$eout);
    vec($rin,$this->sockfileno,1) = 1;
    select($rout=$rin,$wout=$win,$eout=$ein,$timeout);
}

sub get_request_response ($@)
{
    my($this, @oids) = @_;
    return $this->request_response_5 ($this->encode_get_request (@oids),
				      get_response, \@oids, 1);
}

sub set_request_response ($@)
{
    my($this, @pairs) = @_;
    return $this->request_response_5 ($this->encode_set_request (@pairs),
				      get_response, \@pairs, 1);
}

sub getnext_request_response ($@)
{
    my($this,@oids) = @_;
    return $this->request_response_5 ($this->encode_getnext_request (@oids),
				      get_response, \@oids, 1);
}

sub getbulk_request_response ($$$@)
{
    my($this,$non_repeaters,$max_repetitions,@oids) = @_;
    return $this->request_response_5
	($this->encode_getbulk_request ($non_repeaters,$max_repetitions,@oids),
	 get_response, \@oids, 1);
}

sub trap_request_send ($$$$$$@)
{
    my($this, $ent, $agent, $gen, $spec, $dt, @pairs) = @_;
    my($req);

    $req = $this->encode_trap_request ($ent, $agent, $gen, $spec, $dt, @pairs);
    ## Encoding may have returned an error.
    return undef unless defined $req;
    $this->send_query($req)
	|| return $this->error ("send_trap: $!");
    return 1;
}

sub request_response_5 ($$$$$)
{
    my ($this, $req, $response_tag, $oids, $errorp) = @_;
    my $retries = $this->retries;
    my $timeout = $this->timeout;
    my ($nfound, $timeleft);

    ## Encoding may have returned an error.
    return undef unless defined $req;

    $timeleft = $timeout;
    $this->send_query ($req)
	|| return $this->error ("send_query: $!");
    while ($retries > 0) {
	($nfound, $timeleft) = $this->wait_for_response($timeleft);
	if ($nfound > 0) {
	    my($response_length);

	    $response_length
		= $this->receive_response_3 ($response_tag, $oids, $errorp);
	    if ($response_length) {
		return $response_length;
	    } elsif (defined ($response_length)) {
		# A response has been received, but for a different
		# request ID.
	    } else {
		return undef;
	    }
	} else {
	    ## No response received - retry
	    --$retries;
	    $timeout *= $this->backoff;
	    $timeleft = $timeout;
	    $this->send_query ($req)
		|| return $this->error ("send_query: $!");
	}
    }
    $this->error ("no response received");
}


sub error_return ($$)
{
    my ($this,$message) = @_;
    $SNMP_Session::errmsg = $message;
    unless ($SNMP_Session::suppress_warnings) {
	$message =~ s/^/  /mg;
	warn ("Error:\n".$message."\n");
    }
    return undef;
}

sub error ($$)
{
    my ($this,$message) = @_;
    my $session = $this->to_string;
    $SNMP_Session::errmsg = $message."\n".$session;
    unless ($SNMP_Session::suppress_warnings) {
	$session =~ s/^/  /mg;
	$message =~ s/^/  /mg;
	warn ("SNMP Error:\n".$SNMP_Session::errmsg."\n");
    }
    return undef;
}

sub ber_error ($$)
{
  my ($this,$type) = @_;
  my ($errmsg) = $BER::errmsg;

  $errmsg =~ s/^/  /mg;
  return $this->error ("$type:\n$errmsg");
}

sub map_table ($$$) {
    my ($session, $columns, $mapfn) = @_;
    return $session->map_table_4 ($columns, $mapfn,
				  $session->default_max_repetitions ());
}

sub map_table_4 ($$$$) {
    my ($session, $columns, $mapfn, $max_repetitions) = @_;
    return $session->map_table_start_end ($columns, $mapfn,
					  "", undef,
					  $max_repetitions);
}

sub map_table_start_end ($$$$$$) {
    my ($session, $columns, $mapfn, $start, $end, $max_repetitions) = @_;

    my @encoded_oids;
    my $call_counter = 0;
    my $base_index = $start;

    do {
	foreach (@encoded_oids = @{$columns}) {
	    $_=encode_oid (@{$_},split '\.',$base_index)
		|| return $session->ber_error ("encoding OID $base_index");
	}
	if ($session->getnext_request_response (@encoded_oids)) {
	    my $response = $session->pdu_buffer;
	    my ($bindings) = $session->decode_get_response ($response);
	    my $smallest_index = undef;
	    my @collected_values = ();

	    my @bases = @{$columns};
	    while ($bindings ne '') {
		my ($binding, $oid, $value);
		my $base = shift @bases;
		($binding, $bindings) = decode_sequence ($bindings);
		($oid, $value) = decode_by_template ($binding, "%O%@");

		my $out_index;

		$out_index = &oid_diff ($base, $oid);
		my $cmp;
		if (!defined $smallest_index
		    || ($cmp = index_compare ($out_index,$smallest_index)) == -1) {
		    $smallest_index = $out_index;
		    grep ($_=undef, @collected_values);
		    push @collected_values, $value;
		} elsif ($cmp == 1) {
		    push @collected_values, undef;
		} else {
		    push @collected_values, $value;
		}
	    }
	    (++$call_counter,
	     &$mapfn ($smallest_index, @collected_values))
		if defined $smallest_index;
	    $base_index = $smallest_index;
	} else {
	    return undef;
	}
    }
    while (defined $base_index
	   && (!defined $end || index_compare ($base_index, $end) < 0));
    $call_counter;
}