Add an implementation of a SACK scoreboard as per RFC6675.

PiperOrigin-RevId: 220866996
Change-Id: I89d48215df57c00d6a6ec512fc18712a2ea9080b

2 files changed, 12 insertions, 0 deletions

diff --git a/pkg/tcpip/header/BUILD b/pkg/tcpip/header/BUILD
index 66b37720c..8e455fe1e 100644
--- a/pkg/tcpip/header/BUILD
+++ b/pkg/tcpip/header/BUILD
@@ -24,6 +24,7 @@ go_library(
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/seqnum",
+        "@com_github_google_btree//:go_default_library",
     ],
 )
 
diff --git a/pkg/tcpip/header/tcp.go b/pkg/tcpip/header/tcp.go
index 567a21167..207046b36 100644
--- a/pkg/tcpip/header/tcp.go
+++ b/pkg/tcpip/header/tcp.go
@@ -17,6 +17,7 @@ package header
 import (
 	"encoding/binary"
 
+	"github.com/google/btree"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/seqnum"
 )
@@ -131,6 +132,16 @@ type SACKBlock struct {
 	End seqnum.Value
 }
 
+// Less returns true if r.Start < b.Start.
+func (r SACKBlock) Less(b btree.Item) bool {
+	return r.Start.LessThan(b.(SACKBlock).Start)
+}
+
+// Contains returns true if b is completely contained in r.
+func (r SACKBlock) Contains(b SACKBlock) bool {
+	return r.Start.LessThanEq(b.Start) && b.End.LessThanEq(r.End)
+}
+
 // TCPOptions are used to parse and cache the TCP segment options for a non
 // syn/syn-ack segment.
 //