1 .\" SPDX-License-Identifier: Linux-man-pages-1-para
3 .\" This man page is Copyright (C) 1999 Andi Kleen <ak@muc.de>.
5 .\" $Id: rtnetlink.3,v 1.2 1999/05/18 10:35:10 freitag Exp $
7 .TH rtnetlink 3 (date) "Linux man-pages (unreleased)"
9 rtnetlink \- macros to manipulate rtnetlink messages
12 .RI ( libc ", " \-lc )
15 .B #include <asm/types.h>
16 .B #include <linux/netlink.h>
17 .B #include <linux/rtnetlink.h>
18 .B #include <sys/socket.h>
20 .BI "rtnetlink_socket = socket(AF_NETLINK, int " socket_type \
23 .BI "int RTA_OK(struct rtattr *" rta ", int " rtabuflen );
25 .BI "void *RTA_DATA(struct rtattr *" rta );
26 .BI "unsigned int RTA_PAYLOAD(struct rtattr *" rta );
28 .BI "struct rtattr *RTA_NEXT(struct rtattr *" rta \
29 ", unsigned int " rtabuflen );
31 .BI "unsigned int RTA_LENGTH(unsigned int " length );
32 .BI "unsigned int RTA_SPACE(unsigned int "length );
39 message header and appended attributes.
40 The attributes should be manipulated only using the macros provided here.
42 .BI RTA_OK( rta ", " attrlen )
45 points to a valid routing attribute;
47 is the running length of the attribute buffer.
48 When not true then you must assume there are no more attributes in the
54 returns a pointer to the start of this attribute's data.
56 .BI RTA_PAYLOAD( rta )
57 returns the length of this attribute's data.
59 .BI RTA_NEXT( rta ", " attrlen )
60 gets the next attribute after
62 Calling this macro will update
66 to check the validity of the returned pointer.
69 returns the length which is required for
71 bytes of data plus the header.
74 returns the amount of space which will be needed in a message with
80 This manual page is incomplete.
82 .\" FIXME . ? would be better to use libnetlink in the EXAMPLE code here
83 Creating a rtnetlink message to set the MTU of a device:
87 #include <linux/rtnetlink.h>
98 unsigned int mtu = 1000;
100 int rtnetlink_sk = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
102 memset(&req, 0, sizeof(req));
103 req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(req.if));
104 req.nh.nlmsg_flags = NLM_F_REQUEST;
105 req.nh.nlmsg_type = RTM_NEWLINK;
106 req.if.ifi_family = AF_UNSPEC;
107 req.if.ifi_index = INTERFACE_INDEX;
108 req.if.ifi_change = 0xffffffff; /* ??? */
109 rta = (struct rtattr *)(((char *) &req) +
110 NLMSG_ALIGN(req.nh.nlmsg_len));
111 rta\->rta_type = IFLA_MTU;
112 rta\->rta_len = RTA_LENGTH(sizeof(mtu));
113 req.nh.nlmsg_len = NLMSG_ALIGN(req.nh.nlmsg_len) +
114 RTA_LENGTH(sizeof(mtu));
115 memcpy(RTA_DATA(rta), &mtu, sizeof(mtu));
116 send(rtnetlink_sk, &req, req.nh.nlmsg_len, 0);