tools: ynl: add a sample for rt-link

Add a fairly complete example of rt-link usage. If run without any
arguments it simply lists the interfaces and some of their attrs.
If run with an arg it tries to create and delete a netkit device.

 1 # ./tools/net/ynl/samples/rt-link 1
 2 Trying to create a Netkit interface
 3 Testing error message for policy being bad:
 4     Kernel error: 'Provided default xmit policy not supported' (bad attribute: .linkinfo.data(netkit).policy)
 5   1:               lo: mtu 65536
 6   2:           wlp0s1: mtu  1500
 7   3:          enp0s13: mtu  1500
 8   4:           dummy0: mtu  1500  kind dummy     altname one two
 9   5:              nk0: mtu  1500  kind netkit    primary 0  policy forward
10   6:              nk1: mtu  1500  kind netkit    primary 1  policy blackhole
11 Trying to delete a Netkit interface (ifindex 6)

Sample creates the device first, it sets an invalid value for a netkit
attribute to trigger reverse parsing. Line 4 shows the error with the
attribute path correctly generated by YNL.

Then sample fixes the bad attribute and re-issues the request, with
NLM_F_ECHO set. This flag causes the notification to be looped back
to the initiating socket (our socket). Sample parses this notification
to save the ifindex of the created netkit.

Sample then proceeds to list the devices. Line 8 above shows a dummy
device with two alt names. Lines 9 and 10 show the netkit devices
the sample itself created.

The "primary" and "policy" attrs are from inside the netkit submsg.
The string values are auto-generated for the enums by YNL.

To clean up sample deletes the interface it created (line 11).

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250515231650.1325372-10-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/net/ynl/samples/.gitignore b/tools/net/ynl/samples/.gitignore
index 7f9781cf532fd384a07116838426d884b3647cdc..b3ec3fb0929f7f53f42def64d3fd612e47adaed0 100644 (file)
--- a/tools/net/ynl/samples/.gitignore
+++ b/tools/net/ynl/samples/.gitignore
@@ -4,4 +4,5 @@ netdev
 ovs
 page-pool
 rt-addr
+rt-link
 rt-route

diff --git a/tools/net/ynl/samples/rt-link.c b/tools/net/ynl/samples/rt-link.c
new file mode 100644 (file)
index 0000000..acdd4b4
--- /dev/null
+++ b/tools/net/ynl/samples/rt-link.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <string.h>
+
+#include <ynl.h>
+
+#include <arpa/inet.h>
+#include <net/if.h>
+
+#include "rt-link-user.h"
+
+static void rt_link_print(struct rt_link_getlink_rsp *r)
+{
+       unsigned int i;
+
+       printf("%3d: ", r->_hdr.ifi_index);
+
+       if (r->_len.ifname)
+               printf("%16s: ", r->ifname);
+
+       if (r->_present.mtu)
+               printf("mtu %5d  ", r->mtu);
+
+       if (r->linkinfo._len.kind)
+               printf("kind %-8s  ", r->linkinfo.kind);
+       else
+               printf("     %8s  ", "");
+
+       if (r->prop_list._count.alt_ifname) {
+               printf("altname ");
+               for (i = 0; i < r->prop_list._count.alt_ifname; i++)
+                       printf("%s ", r->prop_list.alt_ifname[i]->str);
+               printf(" ");
+       }
+
+       if (r->linkinfo._present.data && r->linkinfo.data._present.netkit) {
+               struct rt_link_linkinfo_netkit_attrs *netkit;
+               const char *name;
+
+               netkit = &r->linkinfo.data.netkit;
+               printf("primary %d  ", netkit->primary);
+
+               name = NULL;
+               if (netkit->_present.policy)
+                       name = rt_link_netkit_policy_str(netkit->policy);
+               if (name)
+                       printf("policy %s  ", name);
+       }
+
+       printf("\n");
+}
+
+static int rt_link_create_netkit(struct ynl_sock *ys)
+{
+       struct rt_link_getlink_ntf *ntf_gl;
+       struct rt_link_newlink_req *req;
+       struct ynl_ntf_base_type *ntf;
+       int ret;
+
+       req = rt_link_newlink_req_alloc();
+       if (!req) {
+               fprintf(stderr, "Can't alloc req\n");
+               return -1;
+       }
+
+       /* rtnetlink doesn't provide info about the created object.
+        * It expects us to set the ECHO flag and the dig the info out
+        * of the notifications...
+        */
+       rt_link_newlink_req_set_nlflags(req, NLM_F_CREATE | NLM_F_ECHO);
+
+       rt_link_newlink_req_set_linkinfo_kind(req, "netkit");
+
+       /* Test error messages */
+       rt_link_newlink_req_set_linkinfo_data_netkit_policy(req, 10);
+       ret = rt_link_newlink(ys, req);
+       if (ret) {
+               printf("Testing error message for policy being bad:\n\t%s\n", ys->err.msg);
+       } else {
+               fprintf(stderr, "Warning: unexpected success creating netkit with bad attrs\n");
+               goto created;
+       }
+
+       rt_link_newlink_req_set_linkinfo_data_netkit_policy(req, NETKIT_DROP);
+
+       ret = rt_link_newlink(ys, req);
+created:
+       rt_link_newlink_req_free(req);
+       if (ret) {
+               fprintf(stderr, "YNL: %s\n", ys->err.msg);
+               return -1;
+       }
+
+       if (!ynl_has_ntf(ys)) {
+               fprintf(stderr,
+                       "Warning: interface created but received no notification, won't delete the interface\n");
+               return 0;
+       }
+
+       ntf = ynl_ntf_dequeue(ys);
+       if (ntf->cmd != RTM_NEWLINK) {
+               fprintf(stderr,
+                       "Warning: unexpected notification type, won't delete the interface\n");
+               return 0;
+       }
+       ntf_gl = (void *)ntf;
+       ret = ntf_gl->obj._hdr.ifi_index;
+       ynl_ntf_free(ntf);
+
+       return ret;
+}
+
+static void rt_link_del(struct ynl_sock *ys, int ifindex)
+{
+       struct rt_link_dellink_req *req;
+
+       req = rt_link_dellink_req_alloc();
+       if (!req) {
+               fprintf(stderr, "Can't alloc req\n");
+               return;
+       }
+
+       req->_hdr.ifi_index = ifindex;
+       if (rt_link_dellink(ys, req))
+               fprintf(stderr, "YNL: %s\n", ys->err.msg);
+       else
+               fprintf(stderr,
+                       "Trying to delete a Netkit interface (ifindex %d)\n",
+                       ifindex);
+
+       rt_link_dellink_req_free(req);
+}
+
+int main(int argc, char **argv)
+{
+       struct rt_link_getlink_req_dump *req;
+       struct rt_link_getlink_list *rsp;
+       struct ynl_error yerr;
+       struct ynl_sock *ys;
+       int created = 0;
+
+       ys = ynl_sock_create(&ynl_rt_link_family, &yerr);
+       if (!ys) {
+               fprintf(stderr, "YNL: %s\n", yerr.msg);
+               return 1;
+       }
+
+       if (argc > 1) {
+               fprintf(stderr, "Trying to create a Netkit interface\n");
+               created = rt_link_create_netkit(ys);
+               if (created < 0)
+                       goto err_destroy;
+       }
+
+       req = rt_link_getlink_req_dump_alloc();
+       if (!req)
+               goto err_del_ifc;
+
+       rsp = rt_link_getlink_dump(ys, req);
+       rt_link_getlink_req_dump_free(req);
+       if (!rsp)
+               goto err_close;
+
+       if (ynl_dump_empty(rsp))
+               fprintf(stderr, "Error: no links reported\n");
+       ynl_dump_foreach(rsp, link)
+               rt_link_print(link);
+       rt_link_getlink_list_free(rsp);
+
+       if (created)
+               rt_link_del(ys, created);
+
+       ynl_sock_destroy(ys);
+       return 0;
+
+err_close:
+       fprintf(stderr, "YNL: %s\n", ys->err.msg);
+err_del_ifc:
+       if (created)
+               rt_link_del(ys, created);
+err_destroy:
+       ynl_sock_destroy(ys);
+       return 2;
+}