gfe-relnote: (n/a) Fix truncated read tests in quic_udp_socket_test.cc under --config=android_arm64. Only affect android build, no behavior change in prod.

Tested=blaze test --config=android_arm64 //third_party/quic/core:quic_udp_socket_test_android_arm64-v8a
PiperOrigin-RevId: 290968630
Change-Id: I64fa368bd45e98732089bdb276a5bae58b188118

quic/core/quic_udp_socket_posix.cc

diff --git a/quic/core/quic_udp_socket_posix.cc b/quic/core/quic_udp_socket_posix.cc
index 6a5f2d9..1141c1c 100644
--- a/quic/core/quic_udp_socket_posix.cc
+++ b/quic/core/quic_udp_socket_posix.cc
@@ -376,7 +376,7 @@
   hdr.msg_control = control_buffer.buffer;
   hdr.msg_controllen = control_buffer.buffer_len;
 
-#if defined(__linux__) && !defined(__ANDROID__)
+#if defined(__linux__)
   // If MSG_TRUNC is set on Linux, recvmsg will return the real packet size even
   // if |packet_buffer| is too small to receive it.
   int flags = MSG_TRUNC;
@@ -399,7 +399,10 @@
     return;
   }
 
-  if (QUIC_PREDICT_FALSE(hdr.msg_flags & MSG_TRUNC)) {
+  if (QUIC_PREDICT_FALSE(hdr.msg_flags & MSG_TRUNC) ||
+      // Normally "bytes_read > packet_buffer.buffer_len" implies the MSG_TRUNC
+      // bit is set, but it is not the case if tested with config=android_arm64.
+      static_cast<size_t>(bytes_read) > packet_buffer.buffer_len) {
     QUIC_LOG_FIRST_N(WARNING, 100)
         << "Received truncated QUIC packet: buffer size:"
         << packet_buffer.buffer_len << " packet size:" << bytes_read;