NAME

       tcp - TCP helper functions

SYNOPSIS

   Modules
       Internal TCP functions

   Functions
       struct tcphdr * nfq_tcp_get_hdr (struct pkt_buff *pktb)
       void * nfq_tcp_get_payload (struct tcphdr *tcph, struct pkt_buff *pktb)
       unsigned int nfq_tcp_get_payload_len (struct tcphdr *tcph, struct pkt_buff *pktb)
       int nfq_tcp_snprintf (char *buf, size_t size, const struct tcphdr *tcph)
       int nfq_tcp_mangle_ipv4 (struct pkt_buff *pktb, unsigned int match_offset, unsigned int
           match_len, const char *rep_buffer, unsigned int rep_len)
       int nfq_tcp_mangle_ipv6 (struct pkt_buff *pktb, unsigned int match_offset, unsigned int
           match_len, const char *rep_buffer, unsigned int rep_len)

Detailed Description

Function Documentation

   struct tcphdr * nfq_tcp_get_hdr (struct pkt_buff * pktb)
       nfq_tcp_get_hdr - get the TCP header

       Parameters
           pktb pointer to user-space network packet buffer

       Returns
           validated pointer to the TCP header or NULL if the TCP header was not set or if a
           minimal length check fails.

       Note
           You have to call nfq_ip_set_transport_header() or nfq_ip6_set_transport_header() first
           to set the TCP header.

       Definition at line 43 of file tcp.c.

   void * nfq_tcp_get_payload (struct tcphdr * tcph, struct pkt_buff * pktb)
       nfq_tcp_get_payload - get the TCP packet payload

       Parameters
           tcph pointer to the TCP header
           pktb pointer to user-space network packet buffer

       Returns
           Pointer to the TCP payload, or NULL if malformed TCP packet.

       Definition at line 62 of file tcp.c.

   unsigned int nfq_tcp_get_payload_len (struct tcphdr * tcph, struct pkt_buff * pktb)
       nfq_tcp_get_payload_len - get the tcp packet payload

       Parameters
           tcph pointer to the TCP header
           pktb pointer to user-space network packet buffer

       Returns
           Length of TCP payload (user data)

       Definition at line 84 of file tcp.c.

   int nfq_tcp_mangle_ipv4 (struct pkt_buff * pktb, unsigned int match_offset, unsigned int
       match_len, const char * rep_buffer, unsigned int rep_len)
       nfq_tcp_mangle_ipv4 - mangle TCP/IPv4 packet buffer

       Parameters
           pktb pointer to network packet buffer
           match_offset 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. See pktb_mangle() for failure case

       Note
           This function updates the IPv4 length and recalculates the IPv4 & TCP checksums for
           you.

       Warning
           After changing the length of a TCP message, the application will need to mangle
           sequence numbers in both directions until another change puts them in sync again

       Definition at line 219 of file tcp.c.

   int nfq_tcp_mangle_ipv6 (struct pkt_buff * pktb, unsigned int match_offset, unsigned int
       match_len, const char * rep_buffer, unsigned int rep_len)
       nfq_tcp_mangle_ipv6 - Mangle TCP/IPv6 packet buffer

       Parameters
           pktb Pointer to network packet buffer
           match_offset Offset from start of TCP data of 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. See pktb_mangle() for failure case

       Note
           This function updates the IPv6 length and recalculates the TCP checksum for you.

       Warning
           After changing the length of a TCP message, the application will need to mangle
           sequence numbers in both directions until another change puts them in sync again

       Definition at line 254 of file tcp.c.

   int nfq_tcp_snprintf (char * buf, size_t size, const struct tcphdr * tcph)
       nfq_pkt_snprintf_tcp_hdr - print tcp header into one buffer in a humnan readable way

       Parameters
           buf pointer to buffer that is used to print the object
           size size of the buffer (or remaining room in it).
           tcph pointer to a valid tcp header.

       Returns
           Same as snprintf

       See also
           snprintf(3)

       Definition at line 160 of file tcp.c.

Author

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