Openvswitch原理与代码分析(7): 添加一条流表flow

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Openvswitch原理与代码分析(7): 添加一条流表flow

2024-08-14 15:34:39 221人阅读

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);
}

Openvswitch原理与代码分析(7): 添加一条流表flow

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Openvswitch原理与代码分析(7): 添加一条流表flow

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