libnl  3.2.24-rc1
Netfilter Library (libnl-nf)

Modules

 Conntrack
 
 Expectation
 
 Log
 
 Queue
 

Socket Creating

int nfnl_connect (struct nl_sock *sk)
 Create and connect netfilter netlink socket. More...
 

Sending

int nfnl_send_simple (struct nl_sock *sk, uint8_t subsys_id, uint8_t type, int flags, uint8_t family, uint16_t res_id)
 Send trivial netfilter netlink message. More...
 

Message Parsing

uint8_t nfnlmsg_subsys (struct nlmsghdr *nlh)
 Get netfilter subsystem id from message. More...
 
uint8_t nfnlmsg_subtype (struct nlmsghdr *nlh)
 Get netfilter message type from message. More...
 
uint8_t nfnlmsg_family (struct nlmsghdr *nlh)
 Get netfilter family from message. More...
 
uint16_t nfnlmsg_res_id (struct nlmsghdr *nlh)
 Get netfilter resource id from message. More...
 

Message Building

struct nl_msg * nfnlmsg_alloc_simple (uint8_t subsys_id, uint8_t type, int flags, uint8_t family, uint16_t res_id)
 Allocate a new netfilter netlink message. More...
 
int nfnlmsg_put (struct nl_msg *msg, uint32_t pid, uint32_t seq, uint8_t subsys_id, uint8_t type, int flags, uint8_t family, uint16_t res_id)
 Add netlink and netfilter netlink headers to netlink message. More...
 

Detailed Description

Message Format
<------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
+----------------------------+- - -+- - - - - - - - - - -+- - -+
| Header | Pad | Payload | Pad |
| struct nlmsghdr | | | |
+----------------------------+- - -+- - - - - - - - - - -+- - -+
<-------- NFNL_HDRLEN --------->
+--------------------------+- - -+------------+
| Netfilter Netlink Header | Pad | Attributes |
| struct nfgenmsg | | |
+--------------------------+- - -+------------+
nfnlmsg_attrdata(nfg, hdrlen)-----^
1) Creating a new netfilter netlink message
struct nl_msg *msg;
// Create a new empty netlink message
msg = nlmsg_alloc();
// Append the netlink and netfilter netlink message header
hdr = nfnlmsg_put(msg, PID, SEQ, SUBSYS, TYPE, NLM_F_ECHO,
FAMILY, RES_ID);
// Append the attributes.
nla_put_u32(msg, 1, 0x10);
// Message is ready to be sent.
// All done? Free the message.
2) Sending of trivial messages
// For trivial messages not requiring any subsys specific header or
// attributes, nfnl_send_simple() may be used to send messages directly.
nfnl_send_simple(sk, SUBSYS, TYPE, 0, FAMILY, RES_ID);

Function Documentation

int nfnl_connect ( struct nl_sock *  sk)

Create and connect netfilter netlink socket.

Parameters
skNetlink socket.

Creates a NETLINK_NETFILTER netlink socket, binds the socket and issues a connection attempt.

See Also
nl_connect()
Returns
0 on success or a negative error code.

Definition at line 84 of file nfnl.c.

References nl_connect().

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int nfnl_send_simple ( struct nl_sock *  sk,
uint8_t  subsys_id,
uint8_t  type,
int  flags,
uint8_t  family,
uint16_t  res_id 
)

Send trivial netfilter netlink message.

Parameters
skNetlink socket.
subsys_idnfnetlink subsystem
typenfnetlink message type
flagsmessage flags
familynfnetlink address family
res_idnfnetlink resource id
Returns
Newly allocated netlink message or NULL.

Definition at line 107 of file nfnl.c.

References nl_send_simple().

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uint8_t nfnlmsg_subsys ( struct nlmsghdr *  nlh)

Get netfilter subsystem id from message.

Parameters
nlhnetlink messsage header

Definition at line 131 of file nfnl.c.

uint8_t nfnlmsg_subtype ( struct nlmsghdr *  nlh)

Get netfilter message type from message.

Parameters
nlhnetlink messsage header

Definition at line 140 of file nfnl.c.

uint8_t nfnlmsg_family ( struct nlmsghdr *  nlh)

Get netfilter family from message.

Parameters
nlhnetlink messsage header

Definition at line 149 of file nfnl.c.

References nlmsg_data().

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uint16_t nfnlmsg_res_id ( struct nlmsghdr *  nlh)

Get netfilter resource id from message.

Parameters
nlhnetlink messsage header

Definition at line 160 of file nfnl.c.

References nlmsg_data().

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struct nl_msg* nfnlmsg_alloc_simple ( uint8_t  subsys_id,
uint8_t  type,
int  flags,
uint8_t  family,
uint16_t  res_id 
)
read

Allocate a new netfilter netlink message.

Parameters
subsys_idnfnetlink subsystem
typenfnetlink message type
flagsmessage flags
familynfnetlink address family
res_idnfnetlink resource id
Returns
Newly allocated netlink message or NULL.

Definition at line 200 of file nfnl.c.

References nlmsg_alloc_simple(), and nlmsg_free().

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int nfnlmsg_put ( struct nl_msg *  msg,
uint32_t  pid,
uint32_t  seq,
uint8_t  subsys_id,
uint8_t  type,
int  flags,
uint8_t  family,
uint16_t  res_id 
)

Add netlink and netfilter netlink headers to netlink message.

Parameters
msgnetlink message
pidnetlink process id
seqsequence number of message
subsys_idnfnetlink subsystem
typenfnetlink message type
flagsmessage flags
familynfnetlink address family
res_idnfnetlink resource id

Definition at line 230 of file nfnl.c.

References nlmsg_put().

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