分片机制的单元测试 手动创建了两个ip报文分片 IP层从链路层获取这两个报文的时候会把它们合并成一个ip报文 这里我们不会继续分发给传输层

而是直接写回 将这个完整的ip报文整个包装 虽然这样在fdbase测试会触发错误（超过了1518），但在channel中并没有这个限制 测试通过 成功合并

tcpip/buffer/prependable.go

@@ -23,7 +23,7 @@ func (p Prependable) UsedLength() int {
 	return len(p.buf) - p.usedIdx
 }
 
-// 从内到外取出报文头的协议
+// 从内到外暴露报文头的协议 eth|ipv4|tcp
 func (p *Prependable) Prepend(size int) []byte {
 	if size > p.usedIdx {
 		return nil

tcpip/network/fragmentation/fragmentation.go

@@ -67,11 +67,25 @@ func (f *Fragmentation) Process(id uint32, first, last uint16, more bool, vv buf
 	}
 	f.mu.Unlock()
 
-	//res, done, consumed := r.process(first, last, more, vv)
-	log.Printf("[%d]的分片 [%d,%d) 合并中\n", id, first, last)
-	r.process(first, last, more, vv)
+	res, done, consumed := r.process(first, last, more, vv)
 
-	return buffer.VectorisedView{}, false
+	f.mu.Lock()
+	f.size += consumed
+	log.Printf("[%d]的分片 [%d,%d] 合并中\n", id, first, last)
+	if done {
+		f.release(r)
+	}
+	// Evict reassemblers if we are consuming more memory than highLimit until
+	// we reach lowLimit.
+	if f.size > f.highLimit {
+		tail := f.rList.Back()
+		for f.size > f.lowLimit && tail != nil {
+			f.release(tail)
+			tail = tail.Prev()
+		}
+	}
+	f.mu.Unlock()
+	return res, done
 }
 
 func (f *Fragmentation) release(r *reassembler) {

tcpip/network/fragmentation/fragmentation_test.go

@@ -162,8 +162,10 @@ func TestFragmentationBase(t *testing.T) {
 	ip.SetChecksum(^ip.CalculateChecksum())
 	copy(v, ip)
 	copy(v[header.IPv4MinimumSize:], payload.First())
-	log.Println(ip.FragmentOffset())
 
 	inject(stackAddr1)
 
+	msg := <-c.linkEP.C
+	log.Println(msg.Header)
+
 }

tcpip/network/fragmentation/reassembler.go

@@ -36,7 +36,7 @@ type reassembler struct {
 	id           uint32
 	size         int
 	mu           sync.Mutex
-	holes        []hole
+	holes        []hole // 每个临时ip报文的缓冲区 最大是65535
 	deleted      int
 	heap         fragHeap // 小根堆用来自动排序
 	done         bool
@@ -68,7 +68,7 @@ func (r *reassembler) updateHoles(first, last uint16, more bool) bool {
 		}
 		used = true
 		r.deleted++
-		r.holes[i].deleted = true
+		r.holes[i].deleted = true // 当前位置被占用
 		if first > r.holes[i].first {
 			r.holes = append(r.holes, hole{r.holes[i].first, first - 1, false})
 		}

tcpip/network/ipv4/ipv4.go

@@ -110,7 +110,8 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload b
 	if protocol == header.ICMPv4ProtocolNumber {
 		log.Printf("IP 写回ICMP报文 长度: %d\n", hdr.UsedLength()+payload.Size())
 	} else {
-		log.Printf("send ipv4 packet %d bytes, proto: 0x%x", hdr.UsedLength()+payload.Size(), protocol)
+		//log.Printf("send ipv4 packet %d bytes, proto: 0x%x", hdr.UsedLength()+payload.Size(), protocol)
+		log.Println(header.IPv4(append(ip, payload.ToView()...)))
 	}
 	return e.linkEP.WritePacket(r, hdr, payload, ProtocolNumber)
 }

tcpip/stack/nic.go

@@ -388,6 +388,8 @@ func (n *NIC) DeliverNetworkPacket(linkEP LinkEndpoint, remoteLinkAddr, localLin
 // transport protocol endpoint.
 func (n *NIC) DeliverTransportPacket(r *Route, protocol tcpip.TransportProtocolNumber, vv buffer.VectorisedView) {
 	log.Println("准备分发传输层数据报")
+	hdr := buffer.NewPrependable(header.EthernetMinimumSize + header.IPv4MinimumSize)
+	r.ref.ep.WritePacket(r, hdr, vv, protocol, 255)
 
 }