tcp可靠性实现 抄了一堆东西 信息量太大了 看不过来

tcpip/header/checksum.go

@@ -33,6 +33,7 @@ func ChecksumCombine(a, b uint16) uint16 {
 // given destination protocol and network address, ignoring the length
 // field. Pseudo-headers are needed by transport layers when calculating
 // their own checksum.
+// hash(protocol, hash(dst, hash(src, 0)))
 func PseudoHeaderChecksum(protocol tcpip.TransportProtocolNumber, srcAddr tcpip.Address, dstAddr tcpip.Address) uint16 {
 	xsum := Checksum([]byte(srcAddr), 0)
 	xsum = Checksum([]byte(dstAddr), xsum)

tcpip/header/tcp.go

@@ -131,6 +131,23 @@ const (
 )
 
 // SACKBlock 表示 sack 块的结构体
+/*
+         +--------+--------+
+         | Kind=5 | Length |
++--------+--------+--------+---------+
+|          Start of 1st Block        |
++--------+--------+--------+---------+
+|           End of 1st Block         |
++--------+--------+--------+---------+
+|                                    |
+/            . . . . . .             /
+|                                    |
++--------+--------+--------+---------+
+|          Start of nth Block        |
++--------+--------+--------+---------+
+|           End of nth Block         |
++--------+--------+--------+---------+
+*/
 type SACKBlock struct {
 	// Start indicates the lowest sequence number in the block.
 	Start seqnum.Value