Change TCPListenSocket::SendInternal to use a non-blocking implementation.

net/base/tcp_listen_socket.cc

Index: net/base/tcp_listen_socket.cc
===================================================================
--- net/base/tcp_listen_socket.cc	(revision 135347)
+++ net/base/tcp_listen_socket.cc	(working copy)
@@ -17,6 +17,7 @@
 #include "net/base/net_errors.h"
 #endif
 
+#include "base/bind.h"
 #include "base/eintr_wrapper.h"
 #include "base/sys_byteorder.h"
 #include "base/threading/platform_thread.h"
@@ -25,6 +26,7 @@
 
 #if defined(OS_WIN)
 typedef int socklen_t;
+#include "net/base/winsock_init.h"
 #endif  // defined(OS_WIN)
 
 namespace net {
@@ -32,7 +34,34 @@
 namespace {
 
 const int kReadBufSize = 4096;
+const int kMaxSendBufSize = 1024 * 1024 * 5;  // 5MB
 
+const net::BackoffEntry::Policy kSendBackoffPolicy = {
+  // Number of initial errors (in sequence) to ignore before applying
+  // exponential back-off rules.
+  0,
+
+  // Initial delay for exponential back-off in ms.
+  25,
+
+  // Factor by which the waiting time will be multiplied.
+  2,
+
+  // Fuzzing percentage. ex: 10% will spread requests randomly
+  // between 90%-100% of the calculated time.
+  0,
+
+  // Maximum amount of time we are willing to delay our request in ms.
+  100,
+
+  // Time to keep an entry from being discarded even when it
+  // has no significant state, -1 to never discard.
+  -1,
+
+  // Don't use initial delay unless the last request was an error.
+  false,
+};
+
 }  // namespace
 
 #if defined(OS_WIN)
@@ -75,7 +104,10 @@
     : ListenSocket(del),
       socket_(s),
       reads_paused_(false),
-      has_pending_reads_(false) {
+      has_pending_reads_(false),
+      send_pending_size_(0),
+      send_error_(false),
+      send_backoff_(&kSendBackoffPolicy) {
 #if defined(OS_WIN)
   socket_event_ = WSACreateEvent();
   // TODO(ibrar): error handling in case of socket_event_ == WSA_INVALID_EVENT
@@ -96,6 +128,10 @@
 }
 
 SOCKET TCPListenSocket::CreateAndBind(const std::string& ip, int port) {
+#if defined(OS_WIN)
+  EnsureWinsockInit();
+#endif
+
   SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
   if (s != kInvalidSocket) {
 #if defined(OS_POSIX)
@@ -132,33 +168,28 @@
 }
 
 void TCPListenSocket::SendInternal(const char* bytes, int len) {
-  char* send_buf = const_cast<char *>(bytes);
-  int len_left = len;
-  while (true) {
-    int sent = HANDLE_EINTR(send(socket_, send_buf, len_left, 0));
-    if (sent == len_left) {  // A shortcut to avoid extraneous checks.
-      break;
-    }
-    if (sent == kSocketError) {
-#if defined(OS_WIN)
-      if (WSAGetLastError() != WSAEWOULDBLOCK) {
-        LOG(ERROR) << "send failed: WSAGetLastError()==" << WSAGetLastError();
-#elif defined(OS_POSIX)
-      if (errno != EWOULDBLOCK && errno != EAGAIN) {
-        LOG(ERROR) << "send failed: errno==" << errno;
-#endif
-        break;
-      }
-      // Otherwise we would block, and now we have to wait for a retry.
-      // Fall through to PlatformThread::YieldCurrentThread()
-    } else {
-      // sent != len_left according to the shortcut above.
-      // Shift the buffer start and send the remainder after a short while.
-      send_buf += sent;
-      len_left -= sent;
-    }
-    base::PlatformThread::YieldCurrentThread();
+  DCHECK(bytes);
+  DCHECK_GT(len, 0);
+
+  if (send_error_)
+    return;
+
+  if (send_pending_size_ + len > kMaxSendBufSize) {
+    // Too much of a backup, stop trying to add more data.

[michaeln, 2012/05/10 16:52:21]

nit: given the log error message immediately below and the easy to read
condition in the if statement, maybe remove this comment

[Marshall, 2012/05/10 19:01:09]

Done.

+    LOG(ERROR) << "send failed: buffer overrun";
+    send_buffers_.clear();
+    send_pending_size_ = 0;
+    send_error_ = true;
+    return;
   }
+
+  scoped_refptr<IOBuffer> buffer(new IOBuffer(len));
+  memcpy(buffer->data(), bytes, len);
+  send_buffers_.push_back(new DrainableIOBuffer(buffer, len));
+  send_pending_size_ += len;
+
+  if (!send_timer_.IsRunning())
+    SendData();
 }
 
 void TCPListenSocket::Listen() {
@@ -319,4 +350,67 @@
 
 #endif
 
+void TCPListenSocket::SendData() {
+  // This method should never be called when the send buffer is empty.

[michaeln, 2012/05/10 16:52:21]

nit: the dcheck effectively says this

[Marshall, 2012/05/10 19:01:09]

Done.

+  DCHECK(!send_buffers_.empty());
+
+  int total_sent = 0;
+
+  // Send data until all buffers have been sent or a call would block.
+  while (!send_buffers_.empty()) {
+    scoped_refptr<DrainableIOBuffer> buffer = send_buffers_.front();
+
+    int len_left = buffer->BytesRemaining();
+    int sent = HANDLE_EINTR(send(socket_, buffer->data(), len_left, 0));
+    DCHECK(sent > 0 || sent == kSocketError);
+
+    if (sent > 0) {
+      if (sent == len_left) {
+        // All data has been sent. Remove the buffer from the list and move on
+        // to the next buffer, if any.
+        send_buffers_.erase(send_buffers_.begin());

[mmenke, 2012/05/10 17:17:19]

nit:  send_buffers_.pop_front()

[Marshall, 2012/05/10 19:01:09]

Done.

+      } else {
+        // The buffer was partially sent.
+        buffer->DidConsume(sent);

[michaeln, 2012/05/10 16:52:21]

style nit: would less text be more readable?

if (sent == len_left)
  send_buffers_.erase(...);
else
  buffer->DidConsume(send);

[Marshall, 2012/05/10 19:01:09]

Done.

+      }
+
+      total_sent += sent;
+    } else if (sent == kSocketError) {
+#if defined(OS_WIN)
+      if (WSAGetLastError() != WSAEWOULDBLOCK) {
+        LOG(ERROR) << "send failed: WSAGetLastError()==" << WSAGetLastError();
+#elif defined(OS_POSIX)
+      if (errno != EWOULDBLOCK && errno != EAGAIN) {
+        LOG(ERROR) << "send failed: errno==" << errno;
+#endif
+        // Don't try to re-send data after a socket error.
+        send_buffers_.clear();
+        send_pending_size_ = 0;
+        send_error_ = true;
+        return;
+      }
+
+      // The call would block. Don't send any more data at this time.
+      break;
+    }
+  }
+
+  if (total_sent > 0) {
+    send_pending_size_ -= total_sent;
+    DCHECK_GE(send_pending_size_, 0);
+
+    // Clear the back-off delay.
+    send_backoff_.Reset();
+  } else {
+    // Increase the back-off delay.
+    send_backoff_.InformOfRequest(false);

[michaeln, 2012/05/10 16:52:21]

the comments about how these affect the back-off delay are useful since the
method names aren't obvious (at least to me)

+  }
+
+  if (!send_buffers_.empty()) {

[michaeln, 2012/05/10 16:52:21]

maybe DCHECK_GT(send_pending_size_, 0)

[Marshall, 2012/05/10 19:01:09]

That's probably not necessary because we DCHECK at the time that we change the
send_pending_size_ value.

+    DCHECK(!send_timer_.IsRunning());
+    send_timer_.Start(FROM_HERE, send_backoff_.GetTimeUntilRelease(),
+                      this, &TCPListenSocket::SendData);
+  }
+}
+
 }  // namespace net