[gssproxy] retry writing to /proc/net/rpc/use-gss-proxy

This improves the handling of cases where the auth_rpcgss module has not yet
been loaded when gssproxy is started.

Signed-off-by: David Härdeman <david@hardeman.nu>

src/gp_init.c

@@ -277,7 +277,7 @@ static void hup_handler(verto_ctx *vctx UNUSED, verto_ev *ev)
     }
 
     /* conditionally reload kernel interface */
-    init_proc_nfsd(gpctx->config);
+    init_proc_nfsd(gpctx);
 
     free_config(&old_config);
 
@@ -376,47 +376,101 @@ int init_event_fini(struct gssproxy_ctx *gpctx)
     return 0;
 }
 
-void init_proc_nfsd(struct gp_config *cfg)
+static int try_init_proc_nfsd(void)
 {
     char buf[] = "1";
-    bool enabled = false;
     int fd, ret;
-    static int poked = 0;
+    static bool poked = false;
+    static bool warned_once = false;
 
-    /* check first if any service enabled kernel support */
-    for (int i = 0; i < cfg->num_svcs; i++) {
-        if (cfg->svcs[i]->kernel_nfsd) {
-            enabled = true;
-            break;
-        }
-    }
-
-    if (!enabled || poked) {
-        return;
-    }
+    if (poked)
+        return 0;
 
     fd = open(LINUX_PROC_USE_GSS_PROXY_FILE, O_RDWR);
     if (fd == -1) {
         ret = errno;
-        GPDEBUG("Kernel doesn't support GSS-Proxy (can't open %s: %d (%s))\n",
-                LINUX_PROC_USE_GSS_PROXY_FILE, ret, gp_strerror(ret));
-        goto fail;
+        if (!warned_once) {
+            GPDEBUG("Kernel doesn't support GSS-Proxy "
+                    "(can't open %s: %d (%s))\n",
+                    LINUX_PROC_USE_GSS_PROXY_FILE, ret, gp_strerror(ret));
+            warned_once = true;
+        }
+        goto out;
     }
 
     ret = write(fd, buf, 1);
     if (ret != 1) {
         ret = errno;
         GPDEBUG("Failed to write to %s: %d (%s)\n",
                 LINUX_PROC_USE_GSS_PROXY_FILE, ret, gp_strerror(ret));
-        close(fd);
-        goto fail;
+        goto out;
     }
 
-    poked = 1;
+    GPDEBUG("Kernel GSS-Proxy support enabled\n");
+    poked = true;
+    ret = 0;
+
+out:
     close(fd);
-    return;
-fail:
-    GPDEBUG("Problem with kernel communication!  NFS server will not work\n");
+    return ret;
+}
+
+static void delayed_proc_nfsd(verto_ctx *vctx UNUSED, verto_ev *ev)
+{
+    struct gssproxy_ctx *gpctx;
+    int ret;
+
+    gpctx = verto_get_private(ev);
+
+    ret = try_init_proc_nfsd();
+    if (ret == 0) {
+        verto_del(gpctx->retry_proc_ev);
+        gpctx->retry_proc_ev = NULL;
+    }
+}
+
+int init_proc_nfsd(struct gssproxy_ctx *gpctx)
+{
+    bool enabled = false;
+    int ret;
+
+    /* check first if any service enabled kernel support */
+    for (int i = 0; i < gpctx->config->num_svcs; i++) {
+        if (gpctx->config->svcs[i]->kernel_nfsd) {
+            enabled = true;
+            break;
+        }
+    }
+
+    if (!enabled) {
+        goto out;
+    }
+
+    ret = try_init_proc_nfsd();
+    if (ret == 0) {
+        goto out;
+    }
+
+    /* failure, but the auth_rpcgss module might not be loaded yet */
+    if (!gpctx->retry_proc_ev) {
+        gpctx->retry_proc_ev = verto_add_timeout(gpctx->vctx,
+                                                 VERTO_EV_FLAG_PERSIST,
+                                                 delayed_proc_nfsd, 10 * 1000);
+        if (!gpctx->retry_proc_ev) {
+            fprintf(stderr, "Failed to register delayed_proc_nfsd event!\n");
+        } else {
+            verto_set_private(gpctx->retry_proc_ev, gpctx, NULL);
+        }
+    }
+
+    return 1;
+
+out:
+    if (gpctx->retry_proc_ev) {
+        verto_del(gpctx->retry_proc_ev);
+        gpctx->retry_proc_ev = NULL;
+    }
+    return 0;
 }
 
 void write_pid(void)

src/gp_proxy.h

@@ -84,6 +84,8 @@ struct gssproxy_ctx {
     time_t term_timeout;
     verto_ev *term_ev; /* termination ev in user mode */
 
+    verto_ev *retry_proc_ev; /* retry telling the kernel to use GSS-Proxy */
+
     ssize_t readstats;
     ssize_t writestats;
     time_t last_activity;
@@ -120,7 +122,7 @@ void fini_server(void);
 int init_sockets(struct gssproxy_ctx *gpctx, struct gp_config *old_config);
 int init_userproxy_socket(struct gssproxy_ctx *gpctx);
 void init_event_loop(struct gssproxy_ctx *gpctx);
-void init_proc_nfsd(struct gp_config *cfg);
+int init_proc_nfsd(struct gssproxy_ctx *gpctx);
 int init_event_fini(struct gssproxy_ctx *gpctx);
 void write_pid(void);
 int drop_privs(struct gp_config *cfg);

src/gssproxy.c

@@ -168,7 +168,7 @@ int main(int argc, const char *argv[])
      * as nfsd needs to know GSS-Proxy is in use before the first time it
      * needs to call accept_sec_context. */
     if (!gpctx->userproxymode) {
-        init_proc_nfsd(gpctx->config);
+        init_proc_nfsd(gpctx);
     }
 
     /* Now it is safe to tell the init system that we're done starting up,