def validate(wire, keyname, secret, now, request_mac, tsig_start, tsig_rdata,
             tsig_rdlen, ctx=None, multi=False, first=True):
    """Validate the specified TSIG rdata against the other input parameters.

    @raises FormError: The TSIG is badly formed.
    @raises BadTime: There is too much time skew between the client and the
    server.
    @raises BadSignature: The TSIG signature did not validate
    @rtype: hmac.HMAC object"""

    (adcount,) = struct.unpack("!H", wire[10:12])
    if adcount == 0:
        raise dns.exception.FormError
    adcount -= 1
    new_wire = wire[0:10] + struct.pack("!H", adcount) + wire[12:tsig_start]
    current = tsig_rdata
    (aname, used) = dns.name.from_wire(wire, current)
    current = current + used
    (upper_time, lower_time, fudge, mac_size) = \
                 struct.unpack("!HIHH", wire[current:current + 10])
    time = ((upper_time + 0L) << 32) + (lower_time + 0L)
    current += 10
    mac = wire[current:current + mac_size]
    current += mac_size
    (original_id, error, other_size) = \
                  struct.unpack("!HHH", wire[current:current + 6])
    current += 6
    other_data = wire[current:current + other_size]
    current += other_size
    if current != tsig_rdata + tsig_rdlen:
        raise dns.exception.FormError
    if error != 0:
        if error == BADSIG:
            raise PeerBadSignature
        elif error == BADKEY:
            raise PeerBadKey
        elif error == BADTIME:
            raise PeerBadTime
        elif error == BADTRUNC:
            raise PeerBadTruncation
        else:
            raise PeerError('unknown TSIG error code %d' % error)
    time_low = time - fudge
    time_high = time + fudge
    if now < time_low or now > time_high:
        raise BadTime
    (junk, our_mac, ctx) = sign(new_wire, keyname, secret, time, fudge,
                                original_id, error, other_data,
                                request_mac, ctx, multi, first, aname)
    if (our_mac != mac):
        raise BadSignature
    return ctx
Validate the specified TSIG rdata against the other input parameters.

    @raises FormError: The TSIG is badly formed.
    @raises BadTime: There is too much time skew between the client and the
    server.
    @raises BadSignature: The TSIG signature did not validate
    @rtype: hmac.HMAC object