commit 3d792e990aa3e8d5c418b2dbea9bb47f698ee90a
author Harald Alvestrand <hta@webrtc.org> Wed Mar 10 07:29:28 2021
committer Commit Bot <commit-bot@chromium.org> Wed Mar 10 20:06:22 2021
tree 2b14dc09faa10d77a6e447580b2b24d6851601cd
parent bccfd26322722cfc46049701e5659239c601af01

Add controls for MTU size of virtual socket server

This will allow us to write tests for what happens when large datagrams
are discarded.

Bug: webrtc:12495
Change-Id: I5c8e9fe55917967ea4604e1b3abe3c590c330ffa
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/211044
Reviewed-by: Taylor <deadbeef@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33425}

rtc_base/virtual_socket_server.cc

diff --git a/rtc_base/virtual_socket_server.cc b/rtc_base/virtual_socket_server.cc
index 043d15a..80d7f3c 100644
--- a/rtc_base/virtual_socket_server.cc
+++ b/rtc_base/virtual_socket_server.cc
@@ -900,7 +900,22 @@
     return -1;
   }
 
+  if (data_size > largest_seen_udp_payload_) {
+    if (data_size > 1000) {
+      RTC_LOG(LS_VERBOSE) << "Largest UDP seen is " << data_size;
+    }
+    largest_seen_udp_payload_ = data_size;
+  }
+
   // See if we want to drop this packet.
+  if (data_size > max_udp_payload_) {
+    RTC_LOG(LS_VERBOSE) << "Dropping too large UDP payload of size "
+                        << data_size << ", UDP payload limit is "
+                        << max_udp_payload_;
+    // Return as if send was successful; packet disappears.
+    return data_size;
+  }
+
   if (Random() < drop_prob_) {
     RTC_LOG(LS_VERBOSE) << "Dropping packet: bad luck";
     return static_cast<int>(data_size);

rtc_base/virtual_socket_server.h

diff --git a/rtc_base/virtual_socket_server.h b/rtc_base/virtual_socket_server.h
index a6e1f64..54de578 100644
--- a/rtc_base/virtual_socket_server.h
+++ b/rtc_base/virtual_socket_server.h
@@ -94,6 +94,16 @@
     drop_prob_ = drop_prob;
   }
 
+  // Controls the maximum UDP payload for the networks simulated
+  // by this server. Any UDP payload sent that is larger than this will
+  // be dropped.
+  size_t max_udp_payload() { return max_udp_payload_; }
+  void set_max_udp_payload(size_t payload_size) {
+    max_udp_payload_ = payload_size;
+  }
+
+  size_t largest_seen_udp_payload() { return largest_seen_udp_payload_; }
+
   // If |blocked| is true, subsequent attempts to send will result in -1 being
   // returned, with the socket error set to EWOULDBLOCK.
   //
@@ -308,6 +318,13 @@
   std::unique_ptr<Function> delay_dist_;
 
   double drop_prob_;
+  // The largest UDP payload permitted on this virtual socket server.
+  // The default is the max size of IPv4 fragmented UDP packet payload:
+  // 65535 bytes - 8 bytes UDP header - 20 bytes IP header.
+  size_t max_udp_payload_ = 65507;
+  // The largest UDP payload seen so far.
+  size_t largest_seen_udp_payload_ = 0;
+
   bool sending_blocked_ = false;
   RTC_DISALLOW_COPY_AND_ASSIGN(VirtualSocketServer);
 };