Add experiment to use ::recvmsg to receive packets on posix systems
Using ::recvmsg ensure packet timestamp can then be read directly when reading the buffer
instead of a separate system call and should also work on Ios/Mac.
The same experiment field trial flag will be "WebRTC-SCM-Timestamp/enabled/" and is also planned to be used for fixing webrtc:14066
Bug: webrtc:5773, webrtc:14066
Change-Id: I8a3749e87c686aa18fcee947472c1b602a0f63c8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/279280
Reviewed-by: Evan Shrubsole <eshr@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38585}
diff --git a/rtc_base/physical_socket_server.cc b/rtc_base/physical_socket_server.cc
index 7c01815..b7d6914 100644
--- a/rtc_base/physical_socket_server.cc
+++ b/rtc_base/physical_socket_server.cc
@@ -52,6 +52,7 @@
#include "rtc_base/null_socket_server.h"
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/time_utils.h"
+#include "system_wrappers/include/field_trial.h"
#if defined(WEBRTC_LINUX)
#include <linux/sockios.h>
@@ -118,6 +119,12 @@
private:
bool* value_;
};
+
+// Returns true if the the client is in the experiment to get timestamps
+// from the socket implementation.
+bool IsScmTimeStampExperimentEnabled() {
+ return webrtc::field_trial::IsEnabled("WebRTC-SCM-Timestamp");
+}
} // namespace
namespace rtc {
@@ -127,7 +134,8 @@
s_(s),
error_(0),
state_((s == INVALID_SOCKET) ? CS_CLOSED : CS_CONNECTED),
- resolver_(nullptr) {
+ resolver_(nullptr),
+ read_scm_timestamp_experiment_(IsScmTimeStampExperimentEnabled()) {
if (s_ != INVALID_SOCKET) {
SetEnabledEvents(DE_READ | DE_WRITE);
@@ -395,7 +403,7 @@
int PhysicalSocket::Recv(void* buffer, size_t length, int64_t* timestamp) {
int received =
- ::recv(s_, static_cast<char*>(buffer), static_cast<int>(length), 0);
+ DoReadFromSocket(buffer, length, /*out_addr*/ nullptr, timestamp);
if ((received == 0) && (length != 0)) {
// Note: on graceful shutdown, recv can return 0. In this case, we
// pretend it is blocking, and then signal close, so that simplifying
@@ -407,9 +415,7 @@
SetError(EWOULDBLOCK);
return SOCKET_ERROR;
}
- if (timestamp) {
- *timestamp = GetSocketRecvTimestamp(s_);
- }
+
UpdateLastError();
int error = GetError();
bool success = (received >= 0) || IsBlockingError(error);
@@ -426,17 +432,8 @@
size_t length,
SocketAddress* out_addr,
int64_t* timestamp) {
- sockaddr_storage addr_storage;
- socklen_t addr_len = sizeof(addr_storage);
- sockaddr* addr = reinterpret_cast<sockaddr*>(&addr_storage);
- int received = ::recvfrom(s_, static_cast<char*>(buffer),
- static_cast<int>(length), 0, addr, &addr_len);
- if (timestamp) {
- *timestamp = GetSocketRecvTimestamp(s_);
- }
+ int received = DoReadFromSocket(buffer, length, out_addr, timestamp);
UpdateLastError();
- if ((received >= 0) && (out_addr != nullptr))
- SocketAddressFromSockAddrStorage(addr_storage, out_addr);
int error = GetError();
bool success = (received >= 0) || IsBlockingError(error);
if (udp_ || success) {
@@ -448,6 +445,84 @@
return received;
}
+int PhysicalSocket::DoReadFromSocket(void* buffer,
+ size_t length,
+ SocketAddress* out_addr,
+ int64_t* timestamp) {
+ sockaddr_storage addr_storage;
+ socklen_t addr_len = sizeof(addr_storage);
+ sockaddr* addr = reinterpret_cast<sockaddr*>(&addr_storage);
+
+#if defined(WEBRTC_POSIX)
+ int received = 0;
+ if (read_scm_timestamp_experiment_) {
+ iovec iov = {.iov_base = buffer, .iov_len = length};
+ msghdr msg = {.msg_iov = &iov, .msg_iovlen = 1};
+ if (out_addr) {
+ out_addr->Clear();
+ msg.msg_name = addr;
+ msg.msg_namelen = addr_len;
+ }
+ char control[CMSG_SPACE(sizeof(struct timeval))] = {};
+ if (timestamp) {
+ *timestamp = -1;
+ msg.msg_control = &control;
+ msg.msg_controllen = sizeof(control);
+ }
+ received = ::recvmsg(s_, &msg, 0);
+ if (received <= 0) {
+ // An error occured or shut down.
+ return received;
+ }
+ if (timestamp) {
+ struct cmsghdr* cmsg;
+ for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+ if (cmsg->cmsg_level != SOL_SOCKET)
+ continue;
+ if (cmsg->cmsg_type == SCM_TIMESTAMP) {
+ timeval* ts = reinterpret_cast<timeval*>(CMSG_DATA(cmsg));
+ *timestamp =
+ rtc::kNumMicrosecsPerSec * static_cast<int64_t>(ts->tv_sec) +
+ static_cast<int64_t>(ts->tv_usec);
+ break;
+ }
+ }
+ }
+ if (out_addr) {
+ SocketAddressFromSockAddrStorage(addr_storage, out_addr);
+ }
+ } else { // !read_scm_timestamp_experiment_
+ if (out_addr) {
+ received = ::recvfrom(s_, static_cast<char*>(buffer),
+ static_cast<int>(length), 0, addr, &addr_len);
+ SocketAddressFromSockAddrStorage(addr_storage, out_addr);
+ } else {
+ received =
+ ::recv(s_, static_cast<char*>(buffer), static_cast<int>(length), 0);
+ }
+ if (timestamp) {
+ *timestamp = GetSocketRecvTimestamp(s_);
+ }
+ }
+ return received;
+
+#else
+ int received = 0;
+ if (out_addr) {
+ received = ::recvfrom(s_, static_cast<char*>(buffer),
+ static_cast<int>(length), 0, addr, &addr_len);
+ SocketAddressFromSockAddrStorage(addr_storage, out_addr);
+ } else {
+ received =
+ ::recv(s_, static_cast<char*>(buffer), static_cast<int>(length), 0);
+ }
+ if (timestamp) {
+ *timestamp = -1;
+ }
+ return received;
+#endif
+}
+
int PhysicalSocket::Listen(int backlog) {
int err = ::listen(s_, backlog);
UpdateLastError();
@@ -643,7 +718,16 @@
ioctlsocket(s_, FIONBIO, &argp);
#elif defined(WEBRTC_POSIX)
fcntl(s_, F_SETFL, fcntl(s_, F_GETFL, 0) | O_NONBLOCK);
+ if (IsScmTimeStampExperimentEnabled()) {
+ int value = 1;
+ // Attempt to get receive packet timestamp from the socket.
+ if (::setsockopt(s_, SOL_SOCKET, SO_TIMESTAMP, &value, sizeof(value)) !=
+ 0) {
+ RTC_DLOG(LS_ERROR) << "::setsockopt failed. errno: " << LAST_SYSTEM_ERROR;
+ }
+ }
#endif
+
#if defined(WEBRTC_IOS)
// iOS may kill sockets when the app is moved to the background
// (specifically, if the app doesn't use the "voip" UIBackgroundMode). When
@@ -651,7 +735,9 @@
// default will terminate the process, which we don't want. By specifying
// this socket option, SIGPIPE will be disabled for the socket.
int value = 1;
- ::setsockopt(s_, SOL_SOCKET, SO_NOSIGPIPE, &value, sizeof(value));
+ if (::setsockopt(s_, SOL_SOCKET, SO_NOSIGPIPE, &value, sizeof(value)) != 0) {
+ RTC_DLOG(LS_ERROR) << "::setsockopt failed. errno: " << LAST_SYSTEM_ERROR;
+ }
#endif
ss_->Add(this);
return true;
