Adds functions to set snd/rcv socket buffer sizes.

Used for non-default 1 MB UDP socket buffers.

src/core/lib/iomgr/socket_utils_common_posix.c

@@ -111,6 +111,16 @@ int grpc_set_socket_ipv6_recvpktinfo_if_possible(int fd) {
 #endif
 }
 
+int grpc_set_socket_sndbuf(int fd, int buffer_size_bytes) {
+  return 0 == setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &buffer_size_bytes,
+                         sizeof(buffer_size_bytes));
+}
+
+int grpc_set_socket_rcvbuf(int fd, int buffer_size_bytes) {
+  return 0 == setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &buffer_size_bytes,
+                         sizeof(buffer_size_bytes));
+}
+
 /* set a socket to close on exec */
 int grpc_set_socket_cloexec(int fd, int close_on_exec) {
   int oldflags = fcntl(fd, F_GETFD, 0);

src/core/lib/iomgr/socket_utils_posix.h

@@ -78,6 +78,14 @@ int grpc_set_socket_ip_pktinfo_if_possible(int fd);
    If IPV6_RECVPKTINFO is not available, returns 1. */
 int grpc_set_socket_ipv6_recvpktinfo_if_possible(int fd);
 
+/* Tries to set the socket's send buffer to given size.
+   Returns 1 on success, 0 on failure. */
+int grpc_set_socket_sndbuf(int fd, int buffer_size_bytes);
+
+/* Tries to set the socket's receive buffer to given size.
+   Returns 1 on success, 0 on failure. */
+int grpc_set_socket_rcvbuf(int fd, int buffer_size_bytes);
+
 /* An enum to keep track of IPv4/IPv6 socket modes.
 
    Currently, this information is only used when a socket is first created, but

src/core/lib/iomgr/udp_server.c

@@ -210,6 +210,8 @@ static int prepare_socket(int fd, const struct sockaddr *addr,
                           size_t addr_len) {
   struct sockaddr_storage sockname_temp;
   socklen_t sockname_len;
+  /* Set send/receive socket buffers to 1 MB */
+  int buffer_size_bytes = 1024 * 1024;
 
   if (fd < 0) {
     goto error;
@@ -239,6 +241,18 @@ static int prepare_socket(int fd, const struct sockaddr *addr,
     goto error;
   }
 
+  if (!grpc_set_socket_sndbuf(fd, buffer_size_bytes)) {
+    gpr_log(GPR_ERROR, "Failed to set send buffer size to %d bytes",
+            buf_size_bytes);
+    goto error;
+  }
+
+  if (!grpc_set_socket_rcvbuf(fd, buffer_size_bytes)) {
+    gpr_log(GPR_ERROR, "Failed to set receive buffer size to %d bytes",
+            buf_size_bytes);
+    goto error;
+  }
+
   return grpc_sockaddr_get_port((struct sockaddr *)&sockname_temp);
 
 error:

test/core/iomgr/fd_posix_test.c

@@ -68,17 +68,15 @@ static void create_test_socket(int port, int *socket_fd,
                                struct sockaddr_in *sin) {
   int fd;
   int one = 1;
-  int buf_size = BUF_SIZE;
+  int buffer_size_bytes = BUF_SIZE;
   int flags;
 
   fd = socket(AF_INET, SOCK_STREAM, 0);
   setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
   /* Reset the size of socket send buffer to the minimal value to facilitate
      buffer filling up and triggering notify_on_write  */
-  GPR_ASSERT(
-      setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &buf_size, sizeof(buf_size)) != -1);
-  GPR_ASSERT(
-      setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &buf_size, sizeof(buf_size)) != -1);
+  GPR_ASSERT(grpc_set_socket_sndbuf(fd, buffer_size_bytes));
+  GPR_ASSERT(grpc_set_socket_rcvbuf(fd, buffer_size_bytes));
   /* Make fd non-blocking */
   flags = fcntl(fd, F_GETFL, 0);
   GPR_ASSERT(fcntl(fd, F_SETFL, flags | O_NONBLOCK) == 0);