Add callback when gRPC FD is about to be orphaned.

src/core/lib/iomgr/udp_server.c

@@ -81,6 +81,7 @@ typedef struct {
   grpc_closure read_closure;
   grpc_closure destroyed_closure;
   grpc_udp_server_read_cb read_cb;
+  grpc_udp_server_orphan_cb orphan_cb;
 } server_port;
 
 /* the overall server */
@@ -168,6 +169,10 @@ static void deactivated_all_ports(grpc_exec_ctx *exec_ctx, grpc_udp_server *s) {
       server_port *sp = &s->ports[i];
       sp->destroyed_closure.cb = destroyed_port;
       sp->destroyed_closure.cb_arg = s;
+
+      GPR_ASSERT(sp->orphan_cb);
+      sp->orphan_cb(sp->emfd);
+
       grpc_fd_orphan(exec_ctx, sp->emfd, &sp->destroyed_closure, NULL,
                      "udp_listener_shutdown");
     }
@@ -268,7 +273,8 @@ static void on_read(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
 
 static int add_socket_to_server(grpc_udp_server *s, int fd,
                                 const struct sockaddr *addr, size_t addr_len,
-                                grpc_udp_server_read_cb read_cb) {
+                                grpc_udp_server_read_cb read_cb,
+                                grpc_udp_server_orphan_cb orphan_cb) {
   server_port *sp;
   int port;
   char *addr_str;
@@ -292,6 +298,7 @@ static int add_socket_to_server(grpc_udp_server *s, int fd,
     memcpy(sp->addr.untyped, addr, addr_len);
     sp->addr_len = addr_len;
     sp->read_cb = read_cb;
+    sp->orphan_cb = orphan_cb;
     GPR_ASSERT(sp->emfd);
     gpr_mu_unlock(&s->mu);
     gpr_free(name);
@@ -301,7 +308,8 @@ static int add_socket_to_server(grpc_udp_server *s, int fd,
 }
 
 int grpc_udp_server_add_port(grpc_udp_server *s, const void *addr,
-                             size_t addr_len, grpc_udp_server_read_cb read_cb) {
+                             size_t addr_len, grpc_udp_server_read_cb read_cb,
+                             grpc_udp_server_orphan_cb orphan_cb) {
   int allocated_port1 = -1;
   int allocated_port2 = -1;
   unsigned i;
@@ -348,7 +356,8 @@ int grpc_udp_server_add_port(grpc_udp_server *s, const void *addr,
     addr = (struct sockaddr *)&wild6;
     addr_len = sizeof(wild6);
     fd = grpc_create_dualstack_socket(addr, SOCK_DGRAM, IPPROTO_UDP, &dsmode);
-    allocated_port1 = add_socket_to_server(s, fd, addr, addr_len, read_cb);
+    allocated_port1 =
+        add_socket_to_server(s, fd, addr, addr_len, read_cb, orphan_cb);
     if (fd >= 0 && dsmode == GRPC_DSMODE_DUALSTACK) {
       goto done;
     }
@@ -370,7 +379,8 @@ int grpc_udp_server_add_port(grpc_udp_server *s, const void *addr,
     addr = (struct sockaddr *)&addr4_copy;
     addr_len = sizeof(addr4_copy);
   }
-  allocated_port2 = add_socket_to_server(s, fd, addr, addr_len, read_cb);
+  allocated_port2 =
+      add_socket_to_server(s, fd, addr, addr_len, read_cb, orphan_cb);
 
 done:
   gpr_free(allocated_addr);

src/core/lib/iomgr/udp_server.h

@@ -48,6 +48,9 @@ typedef struct grpc_udp_server grpc_udp_server;
 typedef void (*grpc_udp_server_read_cb)(grpc_exec_ctx *exec_ctx, grpc_fd *emfd,
                                         struct grpc_server *server);
 
+/* Called when the grpc_fd is about to be orphaned (and the FD closed). */
+typedef void (*grpc_udp_server_orphan_cb)(grpc_fd *emfd);
+
 /* Create a server, initially not bound to any ports */
 grpc_udp_server *grpc_udp_server_create(void);
 
@@ -69,7 +72,8 @@ int grpc_udp_server_get_fd(grpc_udp_server *s, unsigned index);
 /* TODO(ctiller): deprecate this, and make grpc_udp_server_add_ports to handle
                   all of the multiple socket port matching logic in one place */
 int grpc_udp_server_add_port(grpc_udp_server *s, const void *addr,
-                             size_t addr_len, grpc_udp_server_read_cb read_cb);
+                             size_t addr_len, grpc_udp_server_read_cb read_cb,
+                             grpc_udp_server_orphan_cb orphan_cb);
 
 void grpc_udp_server_destroy(grpc_exec_ctx *exec_ctx, grpc_udp_server *server,
                              grpc_closure *on_done);

test/core/iomgr/udp_server_test.c

@@ -54,6 +54,7 @@ static grpc_pollset *g_pollset;
 static gpr_mu *g_mu;
 static int g_number_of_reads = 0;
 static int g_number_of_bytes_read = 0;
+static int g_number_of_orphan_calls = 0;
 
 static void on_read(grpc_exec_ctx *exec_ctx, grpc_fd *emfd,
                     grpc_server *server) {
@@ -71,6 +72,12 @@ static void on_read(grpc_exec_ctx *exec_ctx, grpc_fd *emfd,
   gpr_mu_unlock(g_mu);
 }
 
+static void on_fd_orphaned(grpc_fd *emfd) {
+  gpr_log(GPR_INFO, "gRPC FD about to be orphaned: %d",
+          grpc_fd_wrapped_fd(emfd));
+  g_number_of_orphan_calls++;
+}
+
 static void test_no_op(void) {
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_udp_server *s = grpc_udp_server_create();
@@ -88,6 +95,7 @@ static void test_no_op_with_start(void) {
 }
 
 static void test_no_op_with_port(void) {
+  g_number_of_orphan_calls = 0;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   struct sockaddr_in addr;
   grpc_udp_server *s = grpc_udp_server_create();
@@ -96,13 +104,17 @@ static void test_no_op_with_port(void) {
   memset(&addr, 0, sizeof(addr));
   addr.sin_family = AF_INET;
   GPR_ASSERT(grpc_udp_server_add_port(s, (struct sockaddr *)&addr, sizeof(addr),
-                                      on_read));
+                                      on_read, on_fd_orphaned));
 
   grpc_udp_server_destroy(&exec_ctx, s, NULL);
   grpc_exec_ctx_finish(&exec_ctx);
+
+  /* The server had a single FD, which should be orphaned. */
+  GPR_ASSERT(g_number_of_orphan_calls == 1);
 }
 
 static void test_no_op_with_port_and_start(void) {
+  g_number_of_orphan_calls = 0;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   struct sockaddr_in addr;
   grpc_udp_server *s = grpc_udp_server_create();
@@ -111,12 +123,15 @@ static void test_no_op_with_port_and_start(void) {
   memset(&addr, 0, sizeof(addr));
   addr.sin_family = AF_INET;
   GPR_ASSERT(grpc_udp_server_add_port(s, (struct sockaddr *)&addr, sizeof(addr),
-                                      on_read));
+                                      on_read, on_fd_orphaned));
 
   grpc_udp_server_start(&exec_ctx, s, NULL, 0, NULL);
 
   grpc_udp_server_destroy(&exec_ctx, s, NULL);
   grpc_exec_ctx_finish(&exec_ctx);
+
+  /* The server had a single FD which should be orphaned. */
+  GPR_ASSERT(g_number_of_orphan_calls == 1);
 }
 
 static void test_receive(int number_of_clients) {
@@ -133,11 +148,12 @@ static void test_receive(int number_of_clients) {
   gpr_log(GPR_INFO, "clients=%d", number_of_clients);
 
   g_number_of_bytes_read = 0;
+  g_number_of_orphan_calls = 0;
 
   memset(&addr, 0, sizeof(addr));
   addr.ss_family = AF_INET;
-  GPR_ASSERT(
-      grpc_udp_server_add_port(s, (struct sockaddr *)&addr, addr_len, on_read));
+  GPR_ASSERT(grpc_udp_server_add_port(s, (struct sockaddr *)&addr, addr_len,
+                                      on_read, on_fd_orphaned));
 
   svrfd = grpc_udp_server_get_fd(s, 0);
   GPR_ASSERT(svrfd >= 0);
@@ -176,6 +192,8 @@ static void test_receive(int number_of_clients) {
 
   grpc_udp_server_destroy(&exec_ctx, s, NULL);
   grpc_exec_ctx_finish(&exec_ctx);
+
+  GPR_ASSERT(g_number_of_orphan_calls == 5);
 }
 
 static void destroy_pollset(grpc_exec_ctx *exec_ctx, void *p, bool success) {