Add support for rate limiting out of window ACKs.

Netstack today will send dupACK's with no rate limit for incoming out of
window segments. This can result in ACK loops for example if a TCP socket
connects to itself (actually permitted by TCP). Where the ACK sent in
response to packets being out of order itself gets considered as an out
of window segment resulting in another ACK being generated.

PiperOrigin-RevId: 355206877

1 files changed, 25 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/stack_options.go b/pkg/tcpip/stack/stack_options.go
index 8d9b20b7e..3066f4ffd 100644
--- a/pkg/tcpip/stack/stack_options.go
+++ b/pkg/tcpip/stack/stack_options.go
@@ -15,6 +15,8 @@
 package stack
 
 import (
+	"time"
+
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
@@ -29,6 +31,10 @@ const (
 	// DefaultMaxBufferSize is the default maximum permitted size of a
 	// send/receive buffer.
 	DefaultMaxBufferSize = 4 << 20 // 4 MiB
+
+	// defaultTCPInvalidRateLimit is the default value for
+	// stack.TCPInvalidRateLimit.
+	defaultTCPInvalidRateLimit = 500 * time.Millisecond
 )
 
 // ReceiveBufferSizeOption is used by stack.(Stack*).Option/SetOption to
@@ -39,6 +45,10 @@ type ReceiveBufferSizeOption struct {
 	Max     int
 }
 
+// TCPInvalidRateLimitOption is used by stack.(Stack*).Option/SetOption to get/set
+// stack.tcpInvalidRateLimit.
+type TCPInvalidRateLimitOption time.Duration
+
 // SetOption allows setting stack wide options.
 func (s *Stack) SetOption(option interface{}) tcpip.Error {
 	switch v := option.(type) {
@@ -74,6 +84,15 @@ func (s *Stack) SetOption(option interface{}) tcpip.Error {
 		s.mu.Unlock()
 		return nil
 
+	case TCPInvalidRateLimitOption:
+		if v < 0 {
+			return &tcpip.ErrInvalidOptionValue{}
+		}
+		s.mu.Lock()
+		s.tcpInvalidRateLimit = time.Duration(v)
+		s.mu.Unlock()
+		return nil
+
 	default:
 		return &tcpip.ErrUnknownProtocolOption{}
 	}
@@ -94,6 +113,12 @@ func (s *Stack) Option(option interface{}) tcpip.Error {
 		s.mu.RUnlock()
 		return nil
 
+	case *TCPInvalidRateLimitOption:
+		s.mu.RLock()
+		*v = TCPInvalidRateLimitOption(s.tcpInvalidRateLimit)
+		s.mu.RUnlock()
+		return nil
+
 	default:
 		return &tcpip.ErrUnknownProtocolOption{}
 	}