NAME

       pktbuff - User-space network packet buffer

SYNOPSIS

   Modules
       Other functions

   Functions
       struct pkt_buff * pktb_alloc (int family, void *data, size_t len, size_t extra)
       uint8_t * pktb_data (struct pkt_buff *pktb)
       uint32_t pktb_len (struct pkt_buff *pktb)
       void pktb_free (struct pkt_buff *pktb)
       int pktb_mangle (struct pkt_buff *pktb, int dataoff, unsigned int match_offset, unsigned
           int match_len, const char *rep_buffer, unsigned int rep_len)
       bool pktb_mangled (const struct pkt_buff *pktb)

Detailed Description

       This library provides the user-space network packet buffer. This abstraction is strongly
       inspired by Linux kernel network buffer, the so-called sk_buff.

Function Documentation

   struct pkt_buff * pktb_alloc (int family, void * data, size_t len, size_t extra)
       pktb_alloc - allocate a new packet buffer

       Parameters
           family Indicate what family. Currently supported families are AF_BRIDGE, AF_INET &
           AF_INET6.
           data Pointer to packet data
           len Packet length
           extra Extra memory in the tail to be allocated (for mangling)

       This function returns a packet buffer that contains the packet data and some extra memory
       room in the tail (if requested).

       Returns
           Pointer to a new userspace packet buffer or NULL on failure.

       Errors
           ENOMEM From calloc()
           EPROTONOSUPPORT family was AF_BRIDGE and this is not an IP packet (v4 or v6)

       See also
           calloc(3)

       Definition at line 52 of file pktbuff.c.

   uint8_t * pktb_data (struct pkt_buff * pktb)
       pktb_data - get pointer to network packet

       Parameters
           pktb Pointer to userspace packet buffer

       Returns
           Pointer to start of network packet data within pktb

           It is appropriate to use pktb_data as the second argument of
           nfq_nlmsg_verdict_put_pkt()

       Definition at line 105 of file pktbuff.c.

   void pktb_free (struct pkt_buff * pktb)
       pktb_free - release packet buffer

       Parameters
           pktb Pointer to userspace packet buffer

       Definition at line 129 of file pktbuff.c.

   uint32_t pktb_len (struct pkt_buff * pktb)
       pktb_len - get length of packet buffer

       Parameters
           pktb Pointer to userspace packet buffer

       Returns
           Length of packet contained within pktb

           It is appropriate to use pktb_len as the third argument of nfq_nlmsg_verdict_put_pkt()

       Definition at line 119 of file pktbuff.c.

   int pktb_mangle (struct pkt_buff * pktb, int dataoff, unsigned int match_offset, unsigned int
       match_len, const char * rep_buffer, unsigned int rep_len)
       pktb_mangle - adjust contents of a packet

       Parameters
           pktb Pointer to userspace packet buffer
           dataoff Supplementary offset, usually offset from layer 3 (IP) header to the layer 4
           (TCP or UDP) header. Specify zero to access the layer 3 header. If pktb was created in
           family AF_BRIDGE, specify -ETH_HLEN (a negative offset) to access the layer 2 (MAC)
           header.
           match_offset Further offset to content that you want to mangle
           match_len Length of the existing content you want to mangle
           rep_buffer Pointer to data you want to use to replace current content
           rep_len Length of data you want to use to replace current content

       Returns
           1 for success and 0 for failure. Failure will occur if the extra argument to the
           pktb_alloc() call that created pktb is less than the excess of rep_len over match_len

       Warning
           pktb_mangle does not update any checksums. Developers should use the appropriate
           mangler for the protocol level: nfq_ip_mangle(), nfq_tcp_mangle_ipv4() or
           nfq_udp_mangle_ipv4(). IPv6 versions are planned.
           It is appropriate to use pktb_mangle to change the MAC header.

       Definition at line 314 of file pktbuff.c.

   bool pktb_mangled (const struct pkt_buff * pktb)
       pktb_mangled - test whether packet has been mangled

       Parameters
           pktb Pointer to userspace packet buffer

       Returns
           true if packet has been mangled (modified), else false

           When assembling a verdict, it is not necessary to return the contents of un-modified
           packets. Use pktb_mangled to decide whether packet contents need to be returned.

       Definition at line 359 of file pktbuff.c.

Author

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