.TH "pktbuff" 3 "Thu Jan 28 2021" "Version 1.0.5" "libnetfilter_queue" \" -*- nroff -*-
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.SH NAME
pktbuff \- User-space network packet buffer
.SH SYNOPSIS
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.PP
.SS "Modules"

.in +1c
.ti -1c
.RI "\fBOther functions\fP"
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.in -1c
.SS "Functions"

.in +1c
.ti -1c
.RI "struct pkt_buff * \fBpktb_alloc\fP (int family, void *data, size_t len, size_t extra)"
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.ti -1c
.RI "uint8_t * \fBpktb_data\fP (struct pkt_buff *pktb)"
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.ti -1c
.RI "uint32_t \fBpktb_len\fP (struct pkt_buff *pktb)"
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.ti -1c
.RI "void \fBpktb_free\fP (struct pkt_buff *pktb)"
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.ti -1c
.RI "int \fBpktb_mangle\fP (struct pkt_buff *pktb, int dataoff, unsigned int match_offset, unsigned int match_len, const char *rep_buffer, unsigned int rep_len)"
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.ti -1c
.RI "bool \fBpktb_mangled\fP (const struct pkt_buff *pktb)"
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.in -1c
.SH "Detailed Description"
.PP 
This library provides the user-space network packet buffer\&. This abstraction is strongly inspired by Linux kernel network buffer, the so-called sk_buff\&. 
.SH "Function Documentation"
.PP 
.SS "struct pkt_buff* pktb_alloc (int family, void * data, size_t len, size_t extra)"
pktb_alloc - allocate a new packet buffer 
.PP
\fBParameters\fP
.RS 4
\fIfamily\fP Indicate what family\&. Currently supported families are AF_BRIDGE, AF_INET & AF_INET6\&. 
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\fIdata\fP Pointer to packet data 
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\fIlen\fP Packet length 
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\fIextra\fP Extra memory in the tail to be allocated (for mangling)
.RE
.PP
This function returns a packet buffer that contains the packet data and some extra memory room in the tail (if requested)\&.
.PP
\fBReturns\fP
.RS 4
Pointer to a new userspace packet buffer or NULL on failure\&. 
.RE
.PP
\fBErrors\fP
.RS 4
\fBENOMEM\fP From \fBcalloc\fP() 
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\fBEPROTONOSUPPORT\fP \fIfamily\fP was \fBAF_BRIDGE\fP and this is not an IP packet (v4 or v6) 
.RE
.PP
\fBSee also\fP
.RS 4
\fBcalloc\fP(3) 
.RE
.PP

.PP
Definition at line 52 of file pktbuff\&.c\&.
.SS "uint8_t* pktb_data (struct pkt_buff * pktb)"
pktb_data - get pointer to network packet 
.PP
\fBParameters\fP
.RS 4
\fIpktb\fP Pointer to userspace packet buffer 
.RE
.PP
\fBReturns\fP
.RS 4
Pointer to start of network packet data within \fBpktb\fP 
.RE
.PP
\fB\fP
.RS 4
It is appropriate to use \fIpktb_data\fP as the second argument of \fBnfq_nlmsg_verdict_put_pkt()\fP 
.RE
.PP

.PP
Definition at line 105 of file pktbuff\&.c\&.
.SS "void pktb_free (struct pkt_buff * pktb)"
pktb_free - release packet buffer 
.PP
\fBParameters\fP
.RS 4
\fIpktb\fP Pointer to userspace packet buffer 
.RE
.PP

.PP
Definition at line 129 of file pktbuff\&.c\&.
.SS "uint32_t pktb_len (struct pkt_buff * pktb)"
pktb_len - get length of packet buffer 
.PP
\fBParameters\fP
.RS 4
\fIpktb\fP Pointer to userspace packet buffer 
.RE
.PP
\fBReturns\fP
.RS 4
Length of packet contained within \fBpktb\fP 
.RE
.PP
\fB\fP
.RS 4
It is appropriate to use \fIpktb_len\fP as the third argument of \fBnfq_nlmsg_verdict_put_pkt()\fP 
.RE
.PP

.PP
Definition at line 119 of file pktbuff\&.c\&.
.SS "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 
.PP
\fBParameters\fP
.RS 4
\fIpktb\fP Pointer to userspace packet buffer 
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\fIdataoff\fP 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 \fBpktb\fP was created in family \fBAF_BRIDGE\fP, specify \fB-ETH_HLEN\fP (a negative offset) to access the layer 2 (MAC) header\&. 
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\fImatch_offset\fP Further offset to content that you want to mangle 
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\fImatch_len\fP Length of the existing content you want to mangle 
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\fIrep_buffer\fP Pointer to data you want to use to replace current content 
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\fIrep_len\fP Length of data you want to use to replace current content 
.RE
.PP
\fBReturns\fP
.RS 4
1 for success and 0 for failure\&. Failure will occur if the \fBextra\fP argument to the \fBpktb_alloc()\fP call that created \fBpktb\fP is less than the excess of \fBrep_len\fP over \fBmatch_len\fP 
.RE
.PP
\fBWarning\fP
.RS 4
pktb_mangle does not update any checksums\&. Developers should use the appropriate mangler for the protocol level: \fBnfq_ip_mangle()\fP, \fBnfq_tcp_mangle_ipv4()\fP or \fBnfq_udp_mangle_ipv4()\fP\&. IPv6 versions are planned\&. 
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It is appropriate to use pktb_mangle to change the MAC header\&. 
.RE
.PP

.PP
Definition at line 314 of file pktbuff\&.c\&.
.SS "bool pktb_mangled (const struct pkt_buff * pktb)"
pktb_mangled - test whether packet has been mangled 
.PP
\fBParameters\fP
.RS 4
\fIpktb\fP Pointer to userspace packet buffer 
.RE
.PP
\fBReturns\fP
.RS 4
\fBtrue\fP if packet has been mangled (modified), else \fBfalse\fP 
.RE
.PP
\fB\fP
.RS 4
When assembling a verdict, it is not necessary to return the contents of un-modified packets\&. Use \fIpktb_mangled\fP to decide whether packet contents need to be returned\&. 
.RE
.PP

.PP
Definition at line 359 of file pktbuff\&.c\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for libnetfilter_queue from the source code\&.