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RTNETLINK(3) Linux Programmer’s Manual RTNETLINK(3)
NAME
rtnetlink - Macros to manipuate rtnetlink messages
SYNOPSIS
#include <asm/types.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <sys/socket.h>
rtnetlink_socket = socket(PF_NETLINK, int socket_type, NETLINK_ROUTE);
int RTA_OK(struct rtattr *rta, int rtabuflen);
void *RTA_DATA(struct rtattr *rta);
unsigned int RTA_PAYLOAD(struct rtattr *rta);
struct rtattr *RTA_NEXT(struct rtattr *rta, unsigned int rtabuflen);
unsigned int RTA_LENGTH(unsigned int length);
unsigned int RTA_SPACE(unsigned int length);
DESCRIPTION
All rtnetlink(7) messages consist of a netlink(7) message header and appended
attributes. The attributes should be only manipulated using the macros provided
here.
RTA_OK(rta, attrlen) returns true if rta points to a valid routing attribute;
attrlen is the running length of the attribute buffer. When not true then you
must assume there are no more attributes in the message, even if attrlen is non-
zero.
RTA_DATA(rta) returns a pointer to the start of this attribute’s data.
RTA_PAYLOAD(rta) returns the length of this attribute’s data.
RTA_NEXT(rta, attrlen) gets the next attribute after rta. Calling this macro will
update attrlen. You should use RTA_OK to check for the validity of the returned
pointer.
RTA_LENGTH(len) returns the length which is required for len bytes of data plus the
header.
RTA_SPACE(len) returns the amount of space which will be needed in the message with
len bytes of data.
EXAMPLE
Creating a rtnetlink message to set a MTU of a device.
struct {
struct nlmsghdr nh;
struct ifinfomsg if;
char attrbuf[512];
} req;
struct rtattr *rta;
unsigned int mtu = 1000;
int rtnetlink_sk = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
memset(&req, 0, sizeof(req));
req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
req.nh.nlmsg_flags = NLM_F_REQUEST;
req.nh.nlmsg_type = RTML_NEWLINK;
req.if.ifi_family = AF_UNSPEC;
req.if.ifi_index = INTERFACE_INDEX;
req.if.ifi_change = 0xffffffff; /* ???*/
rta = (struct rtattr *)(((char *) &req) +
NLMSG_ALIGN(n->nlmsg_len));
rta->rta_type = IFLA_MTU;
rta->rta_len = sizeof(unsigned int);
req.n.nlmsg_len = NLMSG_ALIGN(req.n.nlmsg_len) +
RTA_LENGTH(sizeof(mtu));
memcpy(RTA_DATA(rta), &mtu, sizeof (mtu));
send(rtnetlink_sk, &req, req.n.nlmsg_len);
BUGS
This manual page is lacking and incomplete.
SEE ALSO
rtnetlink(7), netlink(7), netlink(3)
Linux Man Page 1999-05-14 RTNETLINK(3)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache/1.3.41 (Unix) PHP/5.2.5 mod_perl/1.30 mod_gzip/1.3.26.1a
Under GNU General Public License
2008-09-06 07:30 @38.103.63.61 CrawledBy CCBot/1.0 (+http://www.commoncrawl.org/bot.html)