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   rtnetlink    ( 3 )

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Имя (Name)

rtnetlink - macros to manipulate rtnetlink messages

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Синопсис (Synopsis)

#include <asm/types.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <sys/socket.h>

rtnetlink_socket = socket(AF_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);

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Описание (Description)

All rtnetlink(7) messages consist of a netlink(7) message header and appended attributes. The attributes should be manipulated only 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 nonzero.

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 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 a message with len bytes of data.

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Стандарты (Conforming to)

These macros are nonstandard Linux extensions.

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Ошибки (баги) (Bugs)

This manual page is incomplete.

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Примеры (Examples)

Creating a rtnetlink message to set the MTU of a device:

           #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);

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Смотри также (See also)

netlink(3), netlink(7), rtnetlink(7)

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