ovs 流表version

插入分类器的流表有一个version字段，类型为struct versions，用来标记此流表在哪个version添加到分类器，如果流表被删除后标记在哪个version被删除。

typedef uint64_t ovs_version_t;#define OVS_VERSION_MIN 0                  /* Default version number to use. */
//可用版本的最大值，为ovs_version_t-1
#define OVS_VERSION_MAX (TYPE_MAXIMUM(ovs_version_t) - 1)
//添加流表时，remove_version被设置此值，表示此流表被添加，还没被删除
#define OVS_VERSION_NOT_REMOVED TYPE_MAXIMUM(ovs_version_t)/** OVS_VERSION_NOT_REMOVED has a special meaning for 'remove_version',* meaning that the rule has been added but not yet removed.*/
struct versions {ovs_version_t add_version;              /* Version object was added in. */ATOMIC(ovs_version_t) remove_version;   /* Version object is removed in. */
};//插入分类器的结构，代表一个流表
struct cls_match {.../* Rule versioning. */struct versions versions;...
};

结构体struct ofproto代表一个ovs网桥，其中字段tables_version用来控制哪些流表可被查询到，每次流表更新都会导致其值增加1。

struct ofproto {...ovs_version_t tables_version;  /* Controls which rules are visible to table lookups. */...
}

struct cls_match的versions字段是在添加流表时被赋值，其中
add_version为当前ofproto->tables_version的值，remove_version为OVS_VERSION_NOT_REMOVED。这样的话，查询流表时，只有ofproto->tables_version在add_version和remove_version范围内的流表才能被匹配。当删除此流表时，add_version值不变，但是remove_version被更新成当前ofproto->tables_version的值，由于ofproto->tables_version的值是不断增长的，所以流表被删除后，ofproto->tables_version的值肯定是大于remove_version的，所以查询流表时，相当于此流表是不可见的。

version的更新

handle_flow_mod__(struct ofproto *ofproto, const struct ofputil_flow_mod *fm, const struct openflow_mod_requester *req)//每次添加，更新或者删除流表 ofproto->tables_version都要加一ofm.version = ofproto->tables_version + 1;//添加流表时，设置 add_version 为 ofm.version，remove_version 为 OVS_VERSION_NOT_REMOVEDofproto_flow_mod_start(ofproto, &ofm);add_flow_start(ofproto, ofm);replace_rule_start(ofproto, ofm, old_rule, new_rule);//将流表插入分类器classifier_insert(&table->cls, &new_rule->cr, ofm->version, ofm->conjs, ofm->n_conjs);classifier_replace(cls, rule, version, conj, n_conj);//分配 cls_match，struct cls_match *new;new = cls_match_alloc(rule, version, conjs, n_conjs);struct cls_match *cls_match = xmalloc(sizeof *cls_match + MINIFLOW_VALUES_SIZE(count));//versions的 add_version 和 remove_version 都被初始化为 version/* Make rule initially invisible. */cls_match->versions = VERSIONS_INITIALIZER(version, version);...//将流表插入分类器后，就可以将 remove_version 设置为 OVS_VERSION_NOT_REMOVED，//可被 classifier_lookup 查询到/* Make 'new' visible to lookups in the appropriate version. */cls_match_set_remove_version(new, OVS_VERSION_NOT_REMOVED);versions_set_remove_version(&rule->versions, version);atomic_store_relaxed(&versions->remove_version, version);//删除流表时，设置 remove_version 为 ofm.version，表示从ofm.version后的版本都不能查询到此流表delete_flow_start_strict(ofproto, ofm);delete_flows_start__(ofproto, ofm->version, rules);struct rule *rule;RULE_COLLECTION_FOR_EACH (rule, rules) {struct oftable *table = &ofproto->tables[rule->table_id];table->n_flows--;//设置 remove_version 为 ofm.version，设置完后后面查找流表时就查不到它了cls_rule_make_invisible_in_version(&rule->cr, version);struct cls_match *cls_match = get_cls_match_protected(rule);cls_match_set_remove_version(cls_match, remove_version);versions_set_remove_version(&rule->versions, version);atomic_store_relaxed(&versions->remove_version, version);}//ofproto->tables_version加1，并更新到 struct ofproto_dpif->tables_versionofproto_bump_tables_version(ofproto);++ofproto->tables_version;ofproto->ofproto_class->set_tables_version(ofproto,ofproto->tables_version);struct ofproto_dpif *ofproto = ofproto_dpif_cast(ofproto_);/* Use memory_order_release to signify that any prior memory accesses can* not be reordered to happen after this atomic store.  This makes sure the* new version is properly set up when the readers can read this 'version'* value. */atomic_store_explicit(&ofproto->tables_version, version, memory_order_release);/* 'need_revalidate' can be reordered to happen before the atomic_store* above, but it does not matter as this variable is not accessed by other* threads. */ofproto->backer->need_revalidate = REV_FLOW_TABLE;

使用version查询流表
只有struct ofproto_dpif->tables_version

//查询流表时，首先获取 struct ofproto_dpif->tables_version，只有此值在流表的 add_version 和 remove_version
//之间的流表才能被匹配
ovs_version_t
ofproto_dpif_get_tables_version(struct ofproto_dpif *ofproto)
{ovs_version_t version;/* Use memory_order_acquire to signify that any following memory accesses* can not be reordered to happen before this atomic read.  This makes sure* all following reads relate to this or a newer version, but never to an* older version. */atomic_read_explicit(&ofproto->tables_version, &version, memory_order_acquire);return version;
}//查询openflow流表
upcall_xlate//ofproto_dpif_get_tables_version获取 ofproto->tables_versionxlate_in_init(&xin, upcall->ofproto,ofproto_dpif_get_tables_version(upcall->ofproto),upcall->flow, upcall->in_port, NULL,stats.tcp_flags, upcall->packet, wc, odp_actions);xin->ofproto = ofproto;xin->tables_version = version;...xlate_actions(&xin, &upcall->xout);struct xlate_ctx ctx = {.xin = xin,...};//开始遍历ofproto的流表rule_dpif_lookup_from_table(ctx.xbridge->ofproto, ctx.xin->tables_version, flow, ctx.wc,ctx.xin->resubmit_stats, &ctx.table_id,flow->in_port.ofp_port, true, true, ctx.xin->xcache);struct rule_dpif *rule;for (next_id = *table_id;next_id < ofproto->up.n_tables;next_id++, next_id += (next_id == TBL_INTERNAL)){*table_id = next_id;rule = rule_dpif_lookup_in_table(ofproto, version, next_id, flow, wc);classifier_lookup(cls, version, flow, wc)classifier_lookup__(cls, version, flow, wc, true);find_match_wc(subtable, version, flow, trie_ctx, cls->n_tries, wc);find_match(subtable, version, flow, hash);//只有可见的流表才能被匹配，//即大于add_version，并且小于remove_version的流表才能被匹配cls_match_visible_in_version(rule, version)versions_visible_in_version(&rule->versions, version);ovs_version_t remove_version;/* C11 does not want to access an atomic via a const object pointer. */atomic_read_relaxed(&CONST_CAST(struct versions *,versions)->remove_version,&remove_version);return versions->add_version <= version && version < remove_version;}

这里还有个疑问，前面说到不管增加还是删除流表ofproto->tables_version是一直增长的，虽然它的类型是uint64_t，是个很大的值，但是如果进程不重启，随着时间拉长，总会溢出反转成0的，这样的话，前面添加的流表就查不到了。

可以做个试验，创建一个网桥，两个namespace，两对veth口，分别连接到网桥和namespace，每个namespace中的veth口配置同网段ip，再添加如下两条流表，此时是可以互相ping通的。

ovs-ofctl add-flow br10 "priority=80, in_port=2, action=1"
ovs-ofctl add-flow br10 "priority=80, in_port=1, action=2"

在添加上面流表时，通过gdb ovs-vswitchd进程，在函数handle_flow_mod__观察到ofproto->tables_version为18和19，
此时两条流表的version分别为

flow1: add_version = 18, remove_version = OVS_VERSION_NOT_REMOVED
flow2: add_version = 19, remove_version = OVS_VERSION_NOT_REMOVED

ofproto->tables_version的值为19，所以在查询流表时，这两条流表是可见的。

但是如果在gdb中强制将ofproto->tables_version改为0，模拟ofproto->tables_version溢出反转的情况，发现两个namespace互相ping不同的。因为ofproto->tables_version不在流表的add_version 和remove_version 范围。查询流表时，查不到这两条流表就会drop报文。

这种情况不太清楚ovs是怎么解决的，莫非就是期望ofproto->tables_version不会溢出反转？知道的同学留个言告知下，多谢

也可参考：ovs 流表version - 简书 (jianshu.com)

ovs 流表version相关推荐

Mellanox CX-5网卡支持OVS流表加速功能的调研
女主宣言本文主要对Mellanox CX-5网卡支持OVS流表加速功能进行了调研,简单介绍了配套软件的版本要求,并描述了整体测试的步骤,另外对其支持VF热迁移也进行了初步的调研,希望对有相同需求的同 ...
OVS 流表轨迹入门及典型场景举例【ovs-appctl ofproto/trace】
OVS 流表轨迹入门及典型场景举例一. 流表轨迹入门二. 典型场景举例三. 小技巧一. 流表轨迹入门在数据中心网络中,SDN控制器通过向OVS交换机下发OpenFlow流表,指导报文转发.在 ...
OVS流表精确匹配TCP/IP报头五元组
---------------- 版权:本文转自cnblogs 刘超的通俗云计算原文链接: https://www.cnblogs.com/popsuper1982/p/5870181.html h ...
OVN 流表基础 -- 基于 kubeOVN （一）
文章目录 Kubectl ko 工具分析 Nbctl Sbctl Trace Ovn 流表 Match Action Register Table 介绍 Logical Switch Datapath ...
Neutron系列 : Neutron OVS OpenFlow 流表和 L2 Population(8)
问题导读: 1.怎样使用arp_responder ? 2.怎样搭建l2pop环境? 3. ARP Responder arp_responder 的原理不复杂.Neutorn DB 中保存了所有的端 ...
ovs 删除openflow流表
有如下三种方法可以删除openflow流表: a. controller/ovs-ofctl主动发命令(OFPFC_DELETE or OFPFC_DELETE_STRICT)删除流表.OFPFC_D ...
ovs 添加流表流程
可以通过controller或者ovs-ofctl命令给网桥添加流表,这篇文章以ovs-ofctl添加流表为例,看一下如何解析匹配域和action,如何发送openflow消息给网桥及ovs-vswi ...
OVS中arp响应的流表的实现
总结: 1.br-int 流表总体是按照Normal 的方式,即常规的交换机的转发方式进行转发.而br-tun 交换机则主要按照流表的方式进行转发. 2.一般情况下,VM发出的ARP请求,会在该VM的 ...
Mininet+OVS：如何更改SDN交换机的流表条目上限
前言流表是SDN交换机转发的重要环节.当一个不匹配的流量进入交换机时,交换机通过packet-in上报控制器,控制器以flow-mod应答,并在交换机中安装对应规则. OVS中提供了对于流表的支持, ...

ovs 流表version

ovs 流表version相关推荐

最新文章

热门文章