ipnetns: add a runtime check for RTM_GETNSID support

The goal of this patch is to test during the runtime if the command RTM_GETNSID
is supported by the kernel.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>

diff --git a/ip/ipnetns.c b/ip/ipnetns.c
index 5a213dcf46cd0b69f775bd5d213cc46c3fc35d43..24df167e9262406399471519522d2bd04b38fc54 100644 (file)
--- a/ip/ipnetns.c
+++ b/ip/ipnetns.c
@@ -34,6 +34,56 @@ static int usage(void)
        exit(-1);
 }
 
+static int have_rtnl_getnsid = -1;
+
+static int ipnetns_accept_msg(const struct sockaddr_nl *who,
+                             struct nlmsghdr *n, void *arg)
+{
+       struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(n);
+
+       if (n->nlmsg_type == NLMSG_ERROR &&
+           (err->error == -EOPNOTSUPP || err->error == -EINVAL))
+               have_rtnl_getnsid = 0;
+       else
+               have_rtnl_getnsid = 1;
+       return -1;
+}
+
+static int ipnetns_have_nsid(void)
+{
+       struct {
+               struct nlmsghdr n;
+               struct rtgenmsg g;
+               char            buf[1024];
+       } req;
+       int fd;
+
+       if (have_rtnl_getnsid < 0) {
+               memset(&req, 0, sizeof(req));
+               req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg));
+               req.n.nlmsg_flags = NLM_F_REQUEST;
+               req.n.nlmsg_type = RTM_GETNSID;
+               req.g.rtgen_family = AF_UNSPEC;
+
+               fd = open("/proc/self/ns/net", O_RDONLY);
+               if (fd < 0) {
+                       perror("open(\"/proc/self/ns/net\")");
+                       exit(1);
+               }
+
+               addattr32(&req.n, 1024, NETNSA_FD, fd);
+
+               if (rtnl_send(&rth, &req.n, req.n.nlmsg_len) < 0) {
+                       perror("request send failed");
+                       exit(1);
+               }
+               rtnl_listen(&rth, ipnetns_accept_msg, NULL);
+               close(fd);
+       }
+
+       return have_rtnl_getnsid;
+}
+
 static int get_netnsid_from_name(const char *name)
 {
        struct {
@@ -95,9 +145,11 @@ static int netns_list(int argc, char **argv)
                if (strcmp(entry->d_name, "..") == 0)
                        continue;
                printf("%s", entry->d_name);
-               id = get_netnsid_from_name(entry->d_name);
-               if (id >= 0)
-                       printf(" (id: %d)", id);
+               if (ipnetns_have_nsid()) {
+                       id = get_netnsid_from_name(entry->d_name);
+                       if (id >= 0)
+                               printf(" (id: %d)", id);
+               }
                printf("\n");
        }
        closedir(dir);