Support SO_REUSEPORT

include/grpc/impl/codegen/grpc_types.h

@@ -154,6 +154,8 @@ typedef struct {
 #define GRPC_SSL_TARGET_NAME_OVERRIDE_ARG "grpc.ssl_target_name_override"
 /* Maximum metadata size */
 #define GRPC_ARG_MAX_METADATA_SIZE "grpc.max_metadata_size"
+/** If non-zero, allow the use of SO_REUSEPORT if it's available (default 1) */
+#define GRPC_ARG_ALLOW_REUSEPORT "grpc.so_reuseport"
 
 /** Result of a grpc call. If the caller satisfies the prerequisites of a
     particular operation, the grpc_call_error returned will be GRPC_CALL_OK.

src/core/ext/transport/chttp2/server/insecure/server_chttp2.c

@@ -102,7 +102,8 @@ int grpc_server_add_insecure_http2_port(grpc_server *server, const char *addr) {
     goto error;
   }
 
-  err = grpc_tcp_server_create(NULL, &tcp);
+  err =
+      grpc_tcp_server_create(NULL, grpc_server_get_channel_args(server), &tcp);
   if (err != GRPC_ERROR_NONE) {
     goto error;
   }

src/core/ext/transport/chttp2/server/secure/server_secure_chttp2.c

@@ -208,7 +208,8 @@ int grpc_server_add_secure_http2_port(grpc_server *server, const char *addr,
   state = gpr_malloc(sizeof(*state));
   memset(state, 0, sizeof(*state));
   grpc_closure_init(&state->destroy_closure, destroy_done, state);
-  err = grpc_tcp_server_create(&state->destroy_closure, &tcp);
+  err = grpc_tcp_server_create(&state->destroy_closure,
+                               grpc_server_get_channel_args(server), &tcp);
   if (err != GRPC_ERROR_NONE) {
     goto error;
   }

src/core/lib/iomgr/socket_utils_common_posix.c

@@ -154,6 +154,28 @@ grpc_error *grpc_set_socket_reuse_addr(int fd, int reuse) {
   return GRPC_ERROR_NONE;
 }
 
+/* set a socket to reuse old addresses */
+grpc_error *grpc_set_socket_reuse_port(int fd, int reuse) {
+#ifndef SO_REUSEPORT
+  return GRPC_ERROR_CREATE("SO_REUSEPORT unavailable on compiling system");
+#else
+  int val = (reuse != 0);
+  int newval;
+  socklen_t intlen = sizeof(newval);
+  if (0 != setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val))) {
+    return GRPC_OS_ERROR(errno, "setsockopt(SO_REUSEPORT)");
+  }
+  if (0 != getsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &newval, &intlen)) {
+    return GRPC_OS_ERROR(errno, "getsockopt(SO_REUSEPORT)");
+  }
+  if ((newval != 0) != val) {
+    return GRPC_ERROR_CREATE("Failed to set SO_REUSEPORT");
+  }
+
+  return GRPC_ERROR_NONE;
+#endif
+}
+
 /* disable nagle */
 grpc_error *grpc_set_socket_low_latency(int fd, int low_latency) {
   int val = (low_latency != 0);

src/core/lib/iomgr/socket_utils_posix.h

@@ -55,6 +55,9 @@ grpc_error *grpc_set_socket_reuse_addr(int fd, int reuse);
 /* disable nagle */
 grpc_error *grpc_set_socket_low_latency(int fd, int low_latency);
 
+/* set SO_REUSEPORT */
+grpc_error *grpc_set_socket_reuse_port(int fd, int reuse);
+
 /* Returns true if this system can create AF_INET6 sockets bound to ::1.
    The value is probed once, and cached for the life of the process.
 

src/core/lib/iomgr/tcp_server.h

@@ -34,6 +34,8 @@
 #ifndef GRPC_CORE_LIB_IOMGR_TCP_SERVER_H
 #define GRPC_CORE_LIB_IOMGR_TCP_SERVER_H
 
+#include <grpc/grpc.h>
+
 #include "src/core/lib/iomgr/closure.h"
 #include "src/core/lib/iomgr/endpoint.h"
 
@@ -58,6 +60,7 @@ typedef void (*grpc_tcp_server_cb)(grpc_exec_ctx *exec_ctx, void *arg,
    If shutdown_complete is not NULL, it will be used by
    grpc_tcp_server_unref() when the ref count reaches zero. */
 grpc_error *grpc_tcp_server_create(grpc_closure *shutdown_complete,
+                                   const grpc_channel_args *args,
                                    grpc_tcp_server **server);
 
 /* Start listening to bound ports */

src/core/lib/iomgr/tcp_server_posix.c

@@ -112,8 +112,10 @@ struct grpc_tcp_server {
   /* destroyed port count: how many ports are completely destroyed */
   size_t destroyed_ports;
 
-  /* is this server shutting down? (boolean) */
-  int shutdown;
+  /* is this server shutting down? */
+  bool shutdown;
+  /* use SO_REUSEPORT */
+  bool so_reuseport;
 
   /* linked list of server ports */
   grpc_tcp_listener *head;
@@ -132,14 +134,42 @@ struct grpc_tcp_server {
   size_t pollset_count;
 };
 
+static gpr_once check_init = GPR_ONCE_INIT;
+static bool has_so_reuseport;
+
+static void init(void) {
+  int s = socket(AF_INET, SOCK_STREAM, 0);
+  if (s >= 0) {
+    has_so_reuseport = GRPC_LOG_IF_ERROR("check for SO_REUSEPORT",
+                                         grpc_set_socket_reuse_port(s, 1));
+    close(s);
+  }
+}
+
 grpc_error *grpc_tcp_server_create(grpc_closure *shutdown_complete,
+                                   const grpc_channel_args *args,
                                    grpc_tcp_server **server) {
+  gpr_once_init(&check_init, init);
+
   grpc_tcp_server *s = gpr_malloc(sizeof(grpc_tcp_server));
+  s->so_reuseport = has_so_reuseport;
+  for (size_t i = 0; i < (args == NULL ? 0 : args->num_args); i++) {
+    if (0 == strcmp(GRPC_ARG_ALLOW_REUSEPORT, args->args[i].key)) {
+      if (args->args[i].type == GRPC_ARG_INTEGER) {
+        s->so_reuseport =
+            has_so_reuseport && (args->args[i].value.integer != 0);
+      } else {
+        gpr_free(s);
+        return GRPC_ERROR_CREATE(GRPC_ARG_ALLOW_REUSEPORT
+                                 " must be an integer");
+      }
+    }
+  }
   gpr_ref_init(&s->refs, 1);
   gpr_mu_init(&s->mu);
   s->active_ports = 0;
   s->destroyed_ports = 0;
-  s->shutdown = 0;
+  s->shutdown = false;
   s->shutdown_starting.head = NULL;
   s->shutdown_starting.tail = NULL;
   s->shutdown_complete = shutdown_complete;
@@ -214,7 +244,7 @@ static void tcp_server_destroy(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
   gpr_mu_lock(&s->mu);
 
   GPR_ASSERT(!s->shutdown);
-  s->shutdown = 1;
+  s->shutdown = true;
 
   /* shutdown all fd's */
   if (s->active_ports) {
@@ -264,13 +294,19 @@ static int get_max_accept_queue_size(void) {
 
 /* Prepare a recently-created socket for listening. */
 static grpc_error *prepare_socket(int fd, const struct sockaddr *addr,
-                                  size_t addr_len, int *port) {
+                                  size_t addr_len, bool so_reuseport,
+                                  int *port) {
   struct sockaddr_storage sockname_temp;
   socklen_t sockname_len;
   grpc_error *err = GRPC_ERROR_NONE;
 
   GPR_ASSERT(fd >= 0);
 
+  if (so_reuseport) {
+    err = grpc_set_socket_reuse_port(fd, 1);
+    if (err != GRPC_ERROR_NONE) goto error;
+  }
+
   err = grpc_set_socket_nonblocking(fd, 1);
   if (err != GRPC_ERROR_NONE) goto error;
   err = grpc_set_socket_cloexec(fd, 1);
@@ -397,7 +433,7 @@ static grpc_error *add_socket_to_server(grpc_tcp_server *s, int fd,
   char *addr_str;
   char *name;
 
-  grpc_error *err = prepare_socket(fd, addr, addr_len, &port);
+  grpc_error *err = prepare_socket(fd, addr, addr_len, s->so_reuseport, &port);
   if (err == GRPC_ERROR_NONE) {
     GPR_ASSERT(port > 0);
     grpc_sockaddr_to_string(&addr_str, (struct sockaddr *)&addr, 1);
@@ -433,6 +469,51 @@ static grpc_error *add_socket_to_server(grpc_tcp_server *s, int fd,
   return err;
 }
 
+static grpc_error *clone_port(grpc_tcp_listener *listener, unsigned count) {
+  grpc_tcp_listener *sp = NULL;
+  char *addr_str;
+  char *name;
+  grpc_error *err;
+
+  for (grpc_tcp_listener *l = listener->next; l && l->is_sibling; l = l->next) {
+    l->fd_index += count;
+  }
+
+  for (unsigned i = 0; i < count; i++) {
+    int fd, port;
+    grpc_dualstack_mode dsmode;
+    err = grpc_create_dualstack_socket(&listener->addr.sockaddr, SOCK_STREAM, 0,
+                                       &dsmode, &fd);
+    if (err != GRPC_ERROR_NONE) return err;
+    err = prepare_socket(fd, &listener->addr.sockaddr, listener->addr_len, true,
+                         &port);
+    if (err != GRPC_ERROR_NONE) return err;
+    grpc_sockaddr_to_string(&addr_str, &listener->addr.sockaddr, 1);
+    gpr_asprintf(&name, "tcp-server-listener:%s/clone-%d", addr_str, i);
+    sp = gpr_malloc(sizeof(grpc_tcp_listener));
+    sp->next = listener->next;
+    listener->next = sp;
+    sp->server = listener->server;
+    sp->fd = fd;
+    sp->emfd = grpc_fd_create(fd, name);
+    memcpy(sp->addr.untyped, listener->addr.untyped, listener->addr_len);
+    sp->addr_len = listener->addr_len;
+    sp->port = port;
+    sp->port_index = listener->port_index;
+    sp->fd_index = listener->fd_index + count - i;
+    sp->is_sibling = 1;
+    sp->sibling = listener->is_sibling ? listener->sibling : listener;
+    GPR_ASSERT(sp->emfd);
+    while (listener->server->tail->next != NULL) {
+      listener->server->tail = listener->server->tail->next;
+    }
+    gpr_free(addr_str);
+    gpr_free(name);
+  }
+
+  return GRPC_ERROR_NONE;
+}
+
 grpc_error *grpc_tcp_server_add_port(grpc_tcp_server *s, const void *addr,
                                      size_t addr_len, int *out_port) {
   grpc_tcp_listener *sp;
@@ -589,14 +670,29 @@ void grpc_tcp_server_start(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s,
   s->on_accept_cb_arg = on_accept_cb_arg;
   s->pollsets = pollsets;
   s->pollset_count = pollset_count;
-  for (sp = s->head; sp; sp = sp->next) {
-    for (i = 0; i < pollset_count; i++) {
-      grpc_pollset_add_fd(exec_ctx, pollsets[i], sp->emfd);
+  sp = s->head;
+  while (sp != NULL) {
+    if (s->so_reuseport && pollset_count > 1) {
+      GPR_ASSERT(GRPC_LOG_IF_ERROR(
+          "clone_port", clone_port(sp, (unsigned)(pollset_count - 1))));
+      for (i = 0; i < pollset_count; i++) {
+        grpc_pollset_add_fd(exec_ctx, pollsets[i], sp->emfd);
+        sp->read_closure.cb = on_read;
+        sp->read_closure.cb_arg = sp;
+        grpc_fd_notify_on_read(exec_ctx, sp->emfd, &sp->read_closure);
+        s->active_ports++;
+        sp = sp->next;
+      }
+    } else {
+      for (i = 0; i < pollset_count; i++) {
+        grpc_pollset_add_fd(exec_ctx, pollsets[i], sp->emfd);
+      }
+      sp->read_closure.cb = on_read;
+      sp->read_closure.cb_arg = sp;
+      grpc_fd_notify_on_read(exec_ctx, sp->emfd, &sp->read_closure);
+      s->active_ports++;
+      sp = sp->next;
     }
-    sp->read_closure.cb = on_read;
-    sp->read_closure.cb_arg = sp;
-    grpc_fd_notify_on_read(exec_ctx, sp->emfd, &sp->read_closure);
-    s->active_ports++;
   }
   gpr_mu_unlock(&s->mu);
 }