Add a SetDoNotFragment() method to DatagramSocket, and call this for

net/udp/udp_socket_posix.h

Index: net/udp/udp_socket_posix.h
diff --git a/net/udp/udp_socket_posix.h b/net/udp/udp_socket_posix.h
index 305c435334ae0c4f27de4f29b72b66671a92207a..8075d911482545a50eeda8606dc9a01ca388dd08 100644
--- a/net/udp/udp_socket_posix.h
+++ b/net/udp/udp_socket_posix.h
@@ -119,6 +119,10 @@ class NET_EXPORT UDPSocketPosix : public base::NonThreadSafe {
   // Returns a net error code.
   int SetSendBufferSize(int32_t size);
 
+  // Configures the socket to set or clear the DF (Do not Fragment) bit on

[Jeremy Dorfman, 2016/08/12 17:23:41]

This can't clear the DF bit now. Also, for IPv6, it prevents hosts from
fragmenting them -- routers aren't allowed to fragment IPv6 packets.

[Ryan Hamilton, 2016/08/12 17:40:53]

Done.

+  // packets, which prevents routers from fragmenting them.
+  int SetDoNotFragment();
+
   // Returns true if the socket is already connected or bound.
   bool is_connected() const { return is_connected_; }