On Sat, Jun 24, 2017 at 04:48:29PM +0800, Hangbin Liu wrote:
> struct {
> struct nlmsghdr hdr;
> - struct rtgenmsg gen;
> + struct ifinfomsg ifm;
> } __attribute__((packed)) request;
>
> memset(&sa, 0, sizeof(sa));
> sa.nl_family = AF_NETLINK;
>
> memset(&request, 0, sizeof(request));
> - request.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(request.gen));
> + request.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(request.ifm));
> request.hdr.nlmsg_type = RTM_GETLINK;
> - request.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
> + request.hdr.nlmsg_flags = NLM_F_REQUEST;
> request.hdr.nlmsg_seq = 1;
> request.hdr.nlmsg_pid = 0;
> - request.gen.rtgen_family = AF_UNSPEC;
> + request.ifm.ifi_family = AF_UNSPEC;
> + request.ifm.ifi_index = if_index;
> + request.ifm.ifi_change = 0xffffffff;
What about portability on older kernel versions? We need to run on
kernels starting with v3.0. The rtnetlink(7) man page says:
struct ifinfomsg {
unsigned char ifi_family; /* AF_UNSPEC */
unsigned short ifi_type; /* Device type */
int ifi_index; /* Interface index */
unsigned int ifi_flags; /* Device flags */
unsigned int ifi_change; /* change mask */
};
ifi_flags contains the device flags, see netdevice(7); ifi_index
is the unique interface index (since Linux 3.7, it is possible
to feed a nonzero value with the RTM_NEWLINK message, thus cre‐
ating a link with the given ifindex); ifi_change is reserved for
future use and should be always set to 0xFFFFFFFF.
If we could always use a per-port rtnl socket, this would be an
improvement. Back when I introduced rtnl, I wrote this:
From 0b3c045a4236f128ab4c1592e6cc91adc1cd6eb0 Mon Sep 17 00:00:00 2001
From: Richard Cochran <[email protected]>
Date: Sun, 31 Jul 2016 12:08:24 +0200
Subject: rtnl: Introduce RT netlink sockets.
This patch adds a source module that implements RT netlink sockets
for the purpose of link monitoring. Unfortunately the netlink API
offers no possibility for per-port notification. Instead it
forces us to use a de-multiplexing pattern.
At that time, I added one extra FD into clock->pollfdp[], and the
clock then farms out the information to the ports. I really did not
to do it that way. A better way would have been to add a new per-port
FD into fd.h, something like this:
enum {
FD_EVENT,
FD_GENERAL,
FD_ANNOUNCE_TIMER,
FD_SYNC_RX_TIMER,
FD_DELAY_TIMER,
FD_QUALIFICATION_TIMER,
FD_MANNO_TIMER,
FD_SYNC_TX_TIMER,
/*here*/ FD_RTNL,
N_POLLFD,
};
struct fdarray {
int fd[N_POLLFD];
};
This would simply your patch set, wouldn't it?
Thanks,
Richard
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