P4语言——basic

练习二：自定义头部

定义一种新的header，实现ipv4转发和自定义头部协议转发的优先级

控制平面代码

下发给交换机table。除了定义ipv4转发的地址与行为匹配，还定义了自定义header的转发行为匹配。

{"target": "bmv2","p4info": "build/basic_tunnel.p4info","bmv2_json": "build/basic_tunnel.json","table_entries": [{"table": "MyIngress.ipv4_lpm","match": {"hdr.ipv4.dstAddr": ["10.0.1.1", 32]},"action_name": "MyIngress.ipv4_forward","action_params": {"dstAddr": "00:00:00:00:01:01","port": 1}},{"table": "MyIngress.ipv4_lpm","match": {"hdr.ipv4.dstAddr": ["10.0.2.2", 32]},"action_name": "MyIngress.ipv4_forward","action_params": {"dstAddr": "00:00:00:02:02:00","port": 2}},{"table": "MyIngress.ipv4_lpm","match": {"hdr.ipv4.dstAddr": ["10.0.3.3", 32]},"action_name": "MyIngress.ipv4_forward","action_params": {"dstAddr": "00:00:00:03:03:00","port": 3}},{"table": "MyIngress.myTunnel_exact","match": {"hdr.myTunnel.dst_id": [1]},"action_name": "MyIngress.myTunnel_forward","action_params": {"port": 1}},{"table": "MyIngress.myTunnel_exact","match": {"hdr.myTunnel.dst_id": [2]},"action_name": "MyIngress.myTunnel_forward","action_params": {"port": 2}},{"table": "MyIngress.myTunnel_exact","match": {"hdr.myTunnel.dst_id": [3]},"action_name": "MyIngress.myTunnel_forward","action_params": {"port": 3}}]
}

拓扑平面代码

{"hosts": ["h1","h2","h3"],"switches": {"s1": { "runtime_json" : "s1-runtime.json" },"s2": { "runtime_json" : "s2-runtime.json" },"s3": { "runtime_json" : "s3-runtime.json" }},"links": [["h1", "s1"], ["s1", "s2"], ["s1", "s3"], ["s3", "s2"], ["s2", "h2"], ["s3", "h3"]]
}

P4文件

/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>const bit<16> TYPE_MYTUNNEL = 0x1212;
const bit<16> TYPE_IPV4 = 0x800;/*************************************************************************
*********************** H E A D E R S  ***********************************
*************************************************************************/typedef bit<9>  egressSpec_t;
typedef bit<48> macAddr_t;
typedef bit<32> ip4Addr_t;header ethernet_t {macAddr_t dstAddr;macAddr_t srcAddr;bit<16>   etherType;
}header myTunnel_t {bit<16> proto_id;bit<16> dst_id;
}header ipv4_t {bit<4>    version;bit<4>    ihl;bit<8>    diffserv;bit<16>   totalLen;bit<16>   identification;bit<3>    flags;bit<13>   fragOffset;bit<8>    ttl;bit<8>    protocol;bit<16>   hdrChecksum;ip4Addr_t srcAddr;ip4Addr_t dstAddr;
}struct metadata {/* empty */
}struct headers {ethernet_t   ethernet;myTunnel_t   myTunnel;ipv4_t       ipv4;
}/*************************************************************************
*********************** P A R S E R  ***********************************
*************************************************************************/parser MyParser(packet_in packet,out headers hdr,inout metadata meta,inout standard_metadata_t standard_metadata) {state start {transition parse_ethernet;}state parse_ethernet {packet.extract(hdr.ethernet);transition select(hdr.ethernet.etherType) {TYPE_MYTUNNEL: parse_myTunnel;//mac层后跟着自定义头部和ipv4头TYPE_IPV4: parse_ipv4;default: accept;}}state parse_myTunnel {packet.extract(hdr.myTunnel);transition select(hdr.myTunnel.proto_id) {TYPE_IPV4: parse_ipv4;//一层层的解析default: accept;}}state parse_ipv4 {packet.extract(hdr.ipv4);transition accept;}}/*************************************************************************
************   C H E C K S U M    V E R I F I C A T I O N   *************
*************************************************************************/control MyVerifyChecksum(inout headers hdr, inout metadata meta) {   apply {  }
}/*************************************************************************
**************  I N G R E S S   P R O C E S S I N G   *******************
*************************************************************************/control MyIngress(inout headers hdr,inout metadata meta,inout standard_metadata_t standard_metadata) {action drop() {mark_to_drop();}action ipv4_forward(macAddr_t dstAddr, egressSpec_t port) {standard_metadata.egress_spec = port;hdr.ethernet.srcAddr = hdr.ethernet.dstAddr;hdr.ethernet.dstAddr = dstAddr;hdr.ipv4.ttl = hdr.ipv4.ttl - 1;}table ipv4_lpm {key = {hdr.ipv4.dstAddr: lpm;}actions = {ipv4_forward;drop;NoAction;}size = 1024;default_action = drop();}action myTunnel_forward(egressSpec_t port) {standard_metadata.egress_spec = port;//根据传入的参数决定端口发送}table myTunnel_exact {key = {hdr.myTunnel.dst_id: exact;}actions = {myTunnel_forward;drop;}size = 1024;default_action = drop();}apply {//如果只有ipv4，根据ipv4转发if (hdr.ipv4.isValid() && !hdr.myTunnel.isValid()) {// Process only non-tunneled IPv4 packetsipv4_lpm.apply();}//如果有自定义头部，根据自定义头部的行为参数转发if (hdr.myTunnel.isValid()) {// process tunneled packetsmyTunnel_exact.apply();}}
}/*************************************************************************
****************  E G R E S S   P R O C E S S I N G   *******************
*************************************************************************/control MyEgress(inout headers hdr,inout metadata meta,inout standard_metadata_t standard_metadata) {apply {  }
}/*************************************************************************
*************   C H E C K S U M    C O M P U T A T I O N   **************
*************************************************************************/control MyComputeChecksum(inout headers  hdr, inout metadata meta) {apply {update_checksum(hdr.ipv4.isValid(),{ hdr.ipv4.version,hdr.ipv4.ihl,hdr.ipv4.diffserv,hdr.ipv4.totalLen,hdr.ipv4.identification,hdr.ipv4.flags,hdr.ipv4.fragOffset,hdr.ipv4.ttl,hdr.ipv4.protocol,hdr.ipv4.srcAddr,hdr.ipv4.dstAddr },hdr.ipv4.hdrChecksum,HashAlgorithm.csum16);}
}/*************************************************************************
***********************  D E P A R S E R  *******************************
*************************************************************************/control MyDeparser(packet_out packet, in headers hdr) {apply {packet.emit(hdr.ethernet);packet.emit(hdr.myTunnel);packet.emit(hdr.ipv4);//重新打包所有header}
}/*************************************************************************
***********************  S W I T C H  *******************************
*************************************************************************/V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;

扩展

如何实现在网络入口增加自定义头部并在网络出口删除自定义头部

增加：对于入口交换机，根据ipv4地址设置自定义header的内容，并设置自定义header为isValid（）。
删除：在出口交换机，根据自定义header设置出口port，并设置自定义header为notValid（）。

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P4语言——basic_tunnel

练习二：自定义头部

控制平面代码

拓扑平面代码

P4文件

扩展

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