309 lines
9.1 KiB
Cython
309 lines
9.1 KiB
Cython
#!/usr/bin/env python3
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import socket
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# Constants for module users
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cdef int COPY_NONE = 0
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cdef int COPY_META = 1
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cdef int COPY_PACKET = 2
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cdef u_int16_t DEFAULT_MAX_QUEUELEN = 1024
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cdef u_int16_t MaxPacketSize = 0xFFFF
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# buffer size - metadata size
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cdef u_int16_t MaxCopySize = 4096 - 80
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# Socket queue should hold max number of packets of copy size bytes
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# formula: DEF_MAX_QUEUELEN * (MaxCopySize+SockOverhead) / 2
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cdef u_int32_t SockRcvSize = 1024 * 4796 // 2
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cdef int nf_callback(nfq_q_handle *qh, nfgenmsg *nfmsg, nfq_data *nfa, void *data) with gil:
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cdef NetfilterQueue nfqueue = <NetfilterQueue>data
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cdef object user_callback = <object>nfqueue.user_callback
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cdef u_int32_t mark
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packet = CPacket()
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with nogil:
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mark = packet.parse(qh, nfa)
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user_callback(packet, mark)
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return 1
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cdef class CPacket:
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'''parent class designed to index/parse full tcp/ip packets (including ethernet). two alternate
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constructors are supplied to support nfqueue or raw sockets.
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raw socket:
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packet = RawPacket.interface(data, address, socket)
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nfqueue:
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packet = RawPacket.netfilter(nfqueue)
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the before_exit method can be overridden to extend the parsing functionality, for example to group
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objects in namedtuples or to index application data.
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'''
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def __cinit__(self):
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self._verdict_is_set = False
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self._mark = 0
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# self.payload = 0
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# def __str__(self):
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# cdef iphdr *hdr = <iphdr*>self.payload
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# protocol = PROTOCOLS.get(hdr.protocol, "Unknown protocol")
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#
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# return "%s packet, %s bytes" % (protocol, self.payload_len)
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# NOTE: this will be callback target for nfqueue
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cdef u_int32_t parse(self, nfq_q_handle *qh, nfq_data *nfa) nogil:
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'''Alternate constructor. Used to start listener/proxy instances using nfqueue bindings.'''
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'''Assign a packet from NFQ to this object. Parse the header and load local values.'''
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self._qh = qh
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self._nfa = nfa
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self._hdr = nfq_get_msg_packet_hdr(nfa)
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self.id = ntohl(self._hdr.packet_id)
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# NOTE: these are not needed at this moment.
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# self.hw_protocol = ntohs(hdr.hw_protocol)
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# self.hook = hdr.hook
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self.data_len = nfq_get_payload(self._nfa, &self.data)
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# TODO: figure this out. cant use no gil if its here.
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# if self.payload_len < 0:
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# raise OSError("Failed to get payload of packet.")
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# timestamp gets assigned via pointer/struct -> time_val: (t_sec, t_usec).
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nfq_get_timestamp(self._nfa, &self.timestamp)
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self._mark = nfq_get_nfmark(nfa)
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return self._mark
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# splitting packet by tcp/ip layers
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self._parse()
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# if (self.continue_condition):
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# self._before_exit()
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cdef void _parse(self) nogil:
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'''Index tcp/ip packet layers 3 & 4 for use as instance objects.
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the before_exit method will be called before returning, which can be used to create
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subclass specific objects like namedtuples or application layer data.'''
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self.ip_header = <iphdr*>self.data
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cdef u_int8_t iphdr_len = (self.ip_header.tos & 15) * 4
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cdef u_int8_t tcphdr_len
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cdef u_int8_t udphdr_len
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if (self.ip_header.protocol == IPPROTO_TCP):
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self.tcp_header = <tcphdr*>self.data[iphdr_len]
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tcphdr_len = (self.tcp_header.th_off & 15) * 4
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self.payload = self.data[iphdr_len+tcphdr_len:self.data_len]
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elif (self.ip_header.protocol == IPPROTO_UDP):
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self.udp_header = <udphdr*>self.data[iphdr_len]
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udphdr_len = 8
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self.payload = self.data[iphdr_len + udphdr_len:self.data_len]
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elif (self.ip_header.protocol == IPPROTO_ICMP):
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self.icmp_header = <icmphdr*>self.data[iphdr_len]
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cdef void verdict(self, u_int32_t verdict):
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'''Call appropriate set_verdict... function on packet.'''
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# TODO: figure out what to do about this. maybe just printf instead?
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if self._verdict_is_set:
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raise RuntimeWarning('Verdict already given for this packet.')
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if self._modified_mark:
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nfq_set_verdict2(
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self._qh, self.id, verdict, self._modified_mark, self.data_len, self.data
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)
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else:
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nfq_set_verdict(
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self._qh, self.id, verdict, self.data_len, self.data
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)
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self._verdict_is_set = True
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def get_raw_packet(self):
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'''returns layer 3-7 of packet data.'''
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return self.data[:self.data_len]
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def get_ip_header(self):
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'''Return layer3 of packet data as a tuple converted directly from C struct.'''
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cdef tuple ip_header
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ip_header = (
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self.ip_header.tos,
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ntohs(self.ip_header.tot_len),
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ntohs(self.ip_header.id),
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self.ip_header.frag_off,
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self.ip_header.ttl,
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ntohs(self.ip_header.protocol),
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self.ip_header.check,
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ntohl(self.ip_header.saddr),
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ntohl(self.ip_header.daddr)
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)
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return ip_header
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def get_proto_header(self):
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'''Return layer4 of packet data as a tuple converted directly from C struct.'''
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cdef tuple proto_header
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if (ip_header.protocol == IPPROTO_TCP):
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proto_header = (
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ntohs(self.tcp_header.th_sport),
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ntohs(self.tcp_header.th_dport),
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ntohl(self.tcp_header.th_seq),
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ntohl(self.tcp_header.th_ack),
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self.tcp_header.th_off,
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self.tcp_header.th_flags,
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ntohs(self.tcp_header.th_win),
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ntohs(self.tcp_header.th_sum),
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self.tcp_header.th_urp
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)
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elif (ip_header.protocol == IPPROTO_UDP):
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proto_header = (
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ntohs(self.udp_header.uh_sport),
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ntohs(self.udp_header.uh_dport),
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ntohs(self.udp_header.uh_ulen),
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ntohs(self.udp_header.uh_sum),
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)
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elif (ip_header.protocol == IPPROTO_ICMP):
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proto_header = (
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self.icmp_header.type,
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)
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return proto_header
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def get_payload(self):
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'''Return payload as Python bytes.'''
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# cdef object payload
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#
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# payload = self.payload
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return self.payload
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# def _before_exit(self):
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# '''executes before returning from parse call.
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# May be overridden.
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# '''
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# pass
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#
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# @property
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# def continue_condition(self):
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# '''controls whether the _before_exit method gets called. must return a boolean.
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# May be overridden.
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# '''
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# return True
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cdef class NetfilterQueue:
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'''Handle a single numbered queue.'''
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def __cinit__(self, *args, **kwargs):
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self.af = kwargs.get('af', PF_INET)
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self.h = nfq_open()
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if self.h == NULL:
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raise OSError('Failed to open NFQueue.')
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# This does NOT kick out previous running queues
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nfq_unbind_pf(self.h, self.af)
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if nfq_bind_pf(self.h, self.af) < 0:
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raise OSError('Failed to bind family %s. Are you root?' % self.af)
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def __dealloc__(self):
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if self.qh != NULL:
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nfq_destroy_queue(self.qh)
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# Don't call nfq_unbind_pf unless you want to disconnect any other
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# processes using this libnetfilter_queue on this protocol family!
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nfq_close(self.h)
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def bind(self, int queue_num, object user_callback, u_int16_t max_len=DEFAULT_MAX_QUEUELEN,
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u_int8_t mode=NFQNL_COPY_PACKET, u_int16_t range=MaxPacketSize, u_int32_t sock_len=SockRcvSize):
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'''Create and bind to a new queue.'''
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cdef unsigned int newsiz
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self.user_callback = user_callback
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self.qh = nfq_create_queue(self.h, queue_num, <nfq_callback*>nf_callback, <void*>self)
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if self.qh == NULL:
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raise OSError(f'Failed to create queue {queue_num}')
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if range > MaxCopySize:
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range = MaxCopySize
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if nfq_set_mode(self.qh, mode, range) < 0:
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raise OSError("Failed to set packet copy mode.")
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nfq_set_queue_maxlen(self.qh, max_len)
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newsiz = nfnl_rcvbufsiz(nfq_nfnlh(self.h), sock_len)
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if newsiz != sock_len * 2:
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raise RuntimeWarning("Socket rcvbuf limit is now %d, requested %d." % (newsiz, sock_len))
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def unbind(self):
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'''Destroy the queue.'''
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if self.qh != NULL:
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nfq_destroy_queue(self.qh)
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self.qh = NULL
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# See warning about nfq _unbind_pf in __dealloc__ above.
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def get_fd(self):
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'''Get the file descriptor of the queue handler.'''
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return nfq_fd(self.h)
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def run(self, bint block=True):
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'''Accept packets using recv.'''
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cdef int fd = self.get_fd()
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cdef char buf[4096]
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cdef int rv
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cdef int recv_flags
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recv_flags = 0
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while True:
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with nogil:
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rv = recv(fd, buf, sizeof(buf), recv_flags)
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if (rv >= 0):
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nfq_handle_packet(self.h, buf, rv)
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else:
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if errno != ENOBUFS:
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break
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