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| -rw-r--r-- | man3/rtnetlink.3 | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/man3/rtnetlink.3 b/man3/rtnetlink.3 new file mode 100644 index 0000000..7033d4b --- /dev/null +++ b/man3/rtnetlink.3 @@ -0,0 +1,122 @@ +.\" SPDX-License-Identifier: Linux-man-pages-1-para +.\" +.\" This man page is Copyright (C) 1999 Andi Kleen <ak@muc.de>. +.\" +.\" $Id: rtnetlink.3,v 1.2 1999/05/18 10:35:10 freitag Exp $ +.\" +.TH rtnetlink 3 2023-07-15 "Linux man-pages 6.05.01" +.SH NAME +rtnetlink \- macros to manipulate rtnetlink messages +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <asm/types.h> +.B #include <linux/netlink.h> +.B #include <linux/rtnetlink.h> +.B #include <sys/socket.h> +.PP +.BI "rtnetlink_socket = socket(AF_NETLINK, int " socket_type \ +", NETLINK_ROUTE);" +.PP +.BI "int RTA_OK(struct rtattr *" rta ", int " rtabuflen ); +.PP +.BI "void *RTA_DATA(struct rtattr *" rta ); +.BI "unsigned int RTA_PAYLOAD(struct rtattr *" rta ); +.PP +.BI "struct rtattr *RTA_NEXT(struct rtattr *" rta \ +", unsigned int " rtabuflen ); +.PP +.BI "unsigned int RTA_LENGTH(unsigned int " length ); +.BI "unsigned int RTA_SPACE(unsigned int "length ); +.fi +.SH DESCRIPTION +All +.BR rtnetlink (7) +messages consist of a +.BR netlink (7) +message header and appended attributes. +The attributes should be manipulated only using the macros provided here. +.PP +.BI RTA_OK( rta ", " attrlen ) +returns true if +.I rta +points to a valid routing attribute; +.I 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 +.I attrlen +is nonzero. +.PP +.BI RTA_DATA( rta ) +returns a pointer to the start of this attribute's data. +.PP +.BI RTA_PAYLOAD( rta ) +returns the length of this attribute's data. +.PP +.BI RTA_NEXT( rta ", " attrlen ) +gets the next attribute after +.IR rta . +Calling this macro will update +.IR attrlen . +You should use +.B RTA_OK +to check the validity of the returned pointer. +.PP +.BI RTA_LENGTH( len ) +returns the length which is required for +.I len +bytes of data plus the header. +.PP +.BI RTA_SPACE( len ) +returns the amount of space which will be needed in a message with +.I len +bytes of data. +.SH STANDARDS +Linux. +.SH BUGS +This manual page is incomplete. +.SH EXAMPLES +.\" FIXME . ? would be better to use libnetlink in the EXAMPLE code here +Creating a rtnetlink message to set the MTU of a device: +.PP +.in +4n +.EX +#include <linux/rtnetlink.h> +\& +\&... +\& +struct { + struct nlmsghdr nh; + struct ifinfomsg if; + char attrbuf[512]; +} req; +\& +struct rtattr *rta; +unsigned int mtu = 1000; +\& +int rtnetlink_sk = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE); +\& +memset(&req, 0, sizeof(req)); +req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(req.if)); +req.nh.nlmsg_flags = NLM_F_REQUEST; +req.nh.nlmsg_type = RTM_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(req.nh.nlmsg_len)); +rta\->rta_type = IFLA_MTU; +rta\->rta_len = RTA_LENGTH(sizeof(mtu)); +req.nh.nlmsg_len = NLMSG_ALIGN(req.nh.nlmsg_len) + + RTA_LENGTH(sizeof(mtu)); +memcpy(RTA_DATA(rta), &mtu, sizeof(mtu)); +send(rtnetlink_sk, &req, req.nh.nlmsg_len, 0); +.EE +.in +.SH SEE ALSO +.BR netlink (3), +.BR netlink (7), +.BR rtnetlink (7) |