Fix handling of unacceptable ACKs during close.

On receiving an ACK with unacceptable ACK number, in a closing state,
TCP, needs to reply back with an ACK with correct seq and ack numbers and
remain in same state. This change is as per RFC793 page 37, but with a
difference that it does not apply to ESTABLISHED state, just as in Linux.
Also add more tests to check for OTW sequence number and unacceptable
ack numbers in these states.

Fixes #3785

PiperOrigin-RevId: 329616283

1 files changed, 9 insertions, 0 deletions

diff --git a/test/packetimpact/dut/posix_server.cc b/test/packetimpact/dut/posix_server.cc
index 2476998f8..de5b4be93 100644
--- a/test/packetimpact/dut/posix_server.cc
+++ b/test/packetimpact/dut/posix_server.cc
@@ -336,6 +336,15 @@ class PosixImpl final : public posix_server::Posix::Service {
     return ::grpc::Status::OK;
   }
 
+  ::grpc::Status Shutdown(grpc_impl::ServerContext *context,
+                          const ::posix_server::ShutdownRequest *request,
+                          ::posix_server::ShutdownResponse *response) override {
+    if (shutdown(request->fd(), request->how()) < 0) {
+      response->set_errno_(errno);
+    }
+    return ::grpc::Status::OK;
+  }
+
   ::grpc::Status Recv(::grpc::ServerContext *context,
                       const ::posix_server::RecvRequest *request,
                       ::posix_server::RecvResponse *response) override {