Openvswitch原理与代码分析(7): 添加一条流表flow

添加一个flow，调用的命令为

ovs-ofctl add-flow hello "hard_timeout=0 idle_timeout=0 priority=1 table=21 pkt_mark=0x55 tun_id=0x55 actions=mod_nw_dst:192.168.56.101,output:2"

这里调用的是调用ovs/utilities/ovs-ofctl.c的命令行工具

这个命令行工具支持的所有的命令及处理函数定义如下：

static const struct ovs_cmdl_command all_commands[] = {     { "show", "switch",       1, 1, ofctl_show },     { "monitor", "switch [misslen] [invalid_ttl] [watch:[...]]",       1, 3, ofctl_monitor },     { "snoop", "switch",       1, 1, ofctl_snoop },     { "dump-desc", "switch",       1, 1, ofctl_dump_desc },     { "dump-tables", "switch",       1, 1, ofctl_dump_tables },     { "dump-table-features", "switch",       1, 1, ofctl_dump_table_features },     { "dump-table-desc", "switch",       1, 1, ofctl_dump_table_desc },     { "dump-flows", "switch",       1, 2, ofctl_dump_flows },     { "dump-aggregate", "switch",       1, 2, ofctl_dump_aggregate },     { "queue-stats", "switch [port [queue]]",       1, 3, ofctl_queue_stats },     { "queue-get-config", "switch port",       2, 2, ofctl_queue_get_config },     { "add-flow", "switch flow",       2, 2, ofctl_add_flow },     { "add-flows", "switch file",       2, 2, ofctl_add_flows },     { "mod-flows", "switch flow",       2, 2, ofctl_mod_flows },     { "del-flows", "switch [flow]",       1, 2, ofctl_del_flows },     { "replace-flows", "switch file",       2, 2, ofctl_replace_flows },     { "diff-flows", "source1 source2",       2, 2, ofctl_diff_flows },     { "add-meter", "switch meter",       2, 2, ofctl_add_meter },     { "mod-meter", "switch meter",       2, 2, ofctl_mod_meter },     { "del-meter", "switch meter",       2, 2, ofctl_del_meters },     { "del-meters", "switch",       1, 1, ofctl_del_meters },     { "dump-meter", "switch meter",       2, 2, ofctl_dump_meters },     { "dump-meters", "switch",       1, 1, ofctl_dump_meters },     { "meter-stats", "switch [meter]",       1, 2, ofctl_meter_stats },     { "meter-features", "switch",       1, 1, ofctl_meter_features },     { "packet-out", "switch in_port actions packet...",       4, INT_MAX, ofctl_packet_out },     { "dump-ports", "switch [port]",       1, 2, ofctl_dump_ports },     { "dump-ports-desc", "switch [port]",       1, 2, ofctl_dump_ports_desc },     { "mod-port", "switch iface act",       3, 3, ofctl_mod_port },     { "mod-table", "switch mod",       3, 3, ofctl_mod_table },     { "get-frags", "switch",       1, 1, ofctl_get_frags },     { "set-frags", "switch frag_mode",       2, 2, ofctl_set_frags },     { "probe", "target",       1, 1, ofctl_probe },     { "ping", "target [n]",       1, 2, ofctl_ping },     { "benchmark", "target n count",       3, 3, ofctl_benchmark },       { "ofp-parse", "file",       1, 1, ofctl_ofp_parse },     { "ofp-parse-pcap", "pcap",       1, INT_MAX, ofctl_ofp_parse_pcap },       { "add-group", "switch group",       1, 2, ofctl_add_group },     { "add-groups", "switch file",       1, 2, ofctl_add_groups },     { "mod-group", "switch group",       1, 2, ofctl_mod_group },     { "del-groups", "switch [group]",       1, 2, ofctl_del_groups },     { "insert-buckets", "switch [group]",       1, 2, ofctl_insert_bucket },     { "remove-buckets", "switch [group]",       1, 2, ofctl_remove_bucket },     { "dump-groups", "switch [group]",       1, 2, ofctl_dump_group_desc },     { "dump-group-stats", "switch [group]",       1, 2, ofctl_dump_group_stats },     { "dump-group-features", "switch",       1, 1, ofctl_dump_group_features },     { "add-tlv-map", "switch map",       2, 2, ofctl_add_tlv_map },     { "del-tlv-map", "switch [map]",       1, 2, ofctl_del_tlv_map },     { "dump-tlv-map", "switch",       1, 1, ofctl_dump_tlv_map },     { "help", NULL, 0, INT_MAX, ofctl_help },     { "list-commands", NULL, 0, INT_MAX, ofctl_list_commands },       /* Undocumented commands for testing. */     { "parse-flow", NULL, 1, 1, ofctl_parse_flow },     { "parse-flows", NULL, 1, 1, ofctl_parse_flows },     { "parse-nx-match", NULL, 0, 0, ofctl_parse_nxm },     { "parse-nxm", NULL, 0, 0, ofctl_parse_nxm },     { "parse-oxm", NULL, 1, 1, ofctl_parse_oxm },     { "parse-actions", NULL, 1, 1, ofctl_parse_actions },     { "parse-instructions", NULL, 1, 1, ofctl_parse_instructions },     { "parse-ofp10-match", NULL, 0, 0, ofctl_parse_ofp10_match },     { "parse-ofp11-match", NULL, 0, 0, ofctl_parse_ofp11_match },     { "parse-pcap", NULL, 1, 1, ofctl_parse_pcap },     { "check-vlan", NULL, 2, 2, ofctl_check_vlan },     { "print-error", NULL, 1, 1, ofctl_print_error },     { "encode-error-reply", NULL, 2, 2, ofctl_encode_error_reply },     { "ofp-print", NULL, 1, 2, ofctl_ofp_print },     { "encode-hello", NULL, 1, 1, ofctl_encode_hello },       { NULL, NULL, 0, 0, NULL }, };

 

根据这个数据结构的定义，"add-flow"调用的函数为

static void ofctl_add_flow(struct ovs_cmdl_context *ctx) {     ofctl_flow_mod(ctx->argc, ctx->argv, OFPFC_ADD); }

 

调用ofctl_flow_mod，parse_ofp_flow_mod_str将字符串解析为ofputil_flow_mod fm

ofputil_flow_mod包含两个最重要的成员变量：

struct match match，所谓match就是一个key。

struct ofpact *ofpacts; /* Series of "struct ofpact"s. */

 

static void ofctl_flow_mod(int argc, char *argv[], uint16_t command) {     if (argc > 2 && !strcmp(argv[2], "-")) {         ofctl_flow_mod_file(argc, argv, command);     } else {         struct ofputil_flow_mod fm;         char *error;         enum ofputil_protocol usable_protocols;           error = parse_ofp_flow_mod_str(&fm, argc > 2 ? argv[2] : "", command,                                        &usable_protocols);         if (error) {             ovs_fatal(0, "%s", error);         }         ofctl_flow_mod__(argv[1], &fm, 1, usable_protocols);     } }

 

ofctl_flow_mod__会打开一个指向ovs-vswitchd的socket，将flow match变成openflow的协议，发出去transact_noreply

static void ofctl_flow_mod__(const char *remote, struct ofputil_flow_mod *fms,                  size_t n_fms, enum ofputil_protocol usable_protocols) {     enum ofputil_protocol protocol;     struct vconn *vconn;     size_t i;       if (bundle) {         bundle_flow_mod__(remote, fms, n_fms, usable_protocols);         return;     }       protocol = open_vconn_for_flow_mod(remote, &vconn, usable_protocols);       for (i = 0; i < n_fms; i++) {         struct ofputil_flow_mod *fm = &fms[i];           transact_noreply(vconn, ofputil_encode_flow_mod(fm, protocol));         free(CONST_CAST(struct ofpact *, fm->ofpacts));     }     vconn_close(vconn); }

 

Ovs-vswitchd会监听socket，在ovs-vswitchd.c中bridge_run每个bridge会监听消息，ofproto_run监听openflow的调用，connmgr_run网络连接管理，ofconn_run管理socket连接。

connmgr_run(p->connmgr, handle_openflow);会设置当有openflow调用的时候，handle_openflow会被调用。

static void handle_openflow(struct ofconn *ofconn, const struct ofpbuf *ofp_msg)     OVS_EXCLUDED(ofproto_mutex) {     enum ofperr error = handle_openflow__(ofconn, ofp_msg);       if (error) {         ofconn_send_error(ofconn, ofp_msg->data, error);     }     COVERAGE_INC(ofproto_recv_openflow); }

 

handle_openflow__会做如下的调用：

case OFPTYPE_FLOW_MOD:     return handle_flow_mod(ofconn, oh);

 

handle_flow_mod首先将openflow协议解析为fm和ofpacts

error = ofputil_decode_flow_mod(&ofm.fm, oh, ofconn_get_protocol(ofconn),                                 &ofpacts,                                 u16_to_ofp(ofproto->max_ports),                                 ofproto->n_tables);

 

然后调用static enum ofperr handle_flow_mod__(struct ofproto *ofproto, struct ofproto_flow_mod *ofm, const struct flow_mod_requester *req)

会调用static enum ofperr ofproto_flow_mod_start(struct ofproto *ofproto, struct ofproto_flow_mod *ofm) OVS_REQUIRES(ofproto_mutex)

static enum ofperr ofproto_flow_mod_start(struct ofproto *ofproto, struct ofproto_flow_mod *ofm)     OVS_REQUIRES(ofproto_mutex) {     switch (ofm->fm.command) {     case OFPFC_ADD:         return add_flow_start(ofproto, ofm);         /* , &be->old_rules.stub[0],            &be->new_rules.stub[0]); */     case OFPFC_MODIFY:         return modify_flows_start_loose(ofproto, ofm);     case OFPFC_MODIFY_STRICT:         return modify_flow_start_strict(ofproto, ofm);     case OFPFC_DELETE:         return delete_flows_start_loose(ofproto, ofm);       case OFPFC_DELETE_STRICT:         return delete_flow_start_strict(ofproto, ofm);     }       return OFPERR_OFPFMFC_BAD_COMMAND; }

 

在函数add_flow_start中，首先cls_rule_init(&cr, &fm->match, fm->priority); 将match也即key变成一个cls_rule，cls_rule是一个压缩版本的match，match是一个整个数据结构保存整个package，从L1一直到L4全都有，比较大，如果保存在内存太浪费，cls_rule中有一个minimatch，是用压缩的方式保存match，也即如果match中为0的部分不保存，采取稀疏矩阵的方式。

接下来创建一个新的rule，error = replace_rule_create(ofproto, fm, &cr, table - ofproto->tables, rule, new_rule);

最后replace_rule_start(ofproto, ofm->version, rule, *new_rule, conjs, n_conjs); 将rule替换现在的rule，有则替换，没有则插入。

static void replace_rule_start(struct ofproto *ofproto, cls_version_t version,                    struct rule *old_rule, struct rule *new_rule,                    struct cls_conjunction *conjs, size_t n_conjs) {     struct oftable *table = &ofproto->tables[new_rule->table_id];       /* 'old_rule' may be either an evicted rule or replaced rule. */     if (old_rule) {         /* Mark the old rule for removal in the next version. */         cls_rule_make_invisible_in_version(&old_rule->cr, version);     } else {         table->n_flows++;     }     /* Insert flow to the classifier, so that later flow_mods may relate      * to it. This is reversible, in case later errors require this to      * be reverted. */     ofproto_rule_insert__(ofproto, new_rule);     /* Make the new rule visible for classifier lookups only from the next      * version. */     classifier_insert(&table->cls, &new_rule->cr, version, conjs, n_conjs); }