默认情况下，每个端口为trunk_mode，并且trunk的vlan为空，报文处理可参考下面的trunk模式。
ovs支持设置的vlan mode如下，可参考ovs-vswitchd.conf.db.5的VLAN Configuration部分。
access模式：
收：
报文带vlan，drop
报文不带vlan，接收，并携带端口的vlan进行后续转发
发：
发出去的报文不带vlan
trunk模式：
收：
报文带vlan，vlan必须在trunk vlan指定的范围或者trunk vlan为空(不用考虑报文携带的vlan)
报文不带vlan，如果trunk vlan不为空，则drop。如果trunk vlan为空，则接收，此为默认情况下的处理。
发：
发出去的报文，带原始vlan
native tagged模式：
收：
报文带vlan，vlan必须在trunk vlan指定的范围或者trunk vlan为空(不用考虑报文携带的vlan)
报文不带vlan，接收，并携带端口的native vlan进行后续转发
发：
发出去的报文，如果报文本来带vlan，则携带原始vlan。如果报文不带vlan，则携带native vlan
native untagged模式：
收：
报文带vlan，vlan必须在trunk vlan指定的范围或者trunk vlan为空(不用考虑报文携带的vlan)
报文不带vlan，接收，并携带端口的native vlan进行后续转发
发：
发出去的报文，如果报文本来带vlan，则携带原始vlan。如果报文不带vlan，则报文也不带vlan
配置vlan流程
通过命令行配置端口的vlan模式和tag信息时，最终会调用port_configure，此函数会将从ovsdb-server接收的端口配置信息提取出来，再调用bundle_set将相关信息填充到struct ofbundle，并将struct ofbundle插入hash表ofproto->bundles。
static void
port_configure(struct port *port)
{
const struct ovsrec_port *cfg = port->cfg;
struct ofproto_bundle_settings s;
struct iface *iface;
/* Get name. */
s.name = port->name;
/* Get slaves. */
s.n_slaves = 0;
s.slaves = xmalloc(ovs_list_size(&port->ifaces) * sizeof *s.slaves);
LIST_FOR_EACH (iface, port_elem, &port->ifaces) {
s.slaves[s.n_slaves++] = iface->ofp_port;
}
/* Get VLAN tag. */
s.vlan = -1;
if (cfg->tag && *cfg->tag >= 0 && *cfg->tag <= 4095) {
s.vlan = *cfg->tag;
}
/* Get VLAN trunks. */
s.trunks = NULL;
if (cfg->n_trunks) {
s.trunks = vlan_bitmap_from_array(cfg->trunks, cfg->n_trunks);
}
s.cvlans = NULL;
if (cfg->n_cvlans) {
s.cvlans = vlan_bitmap_from_array(cfg->cvlans, cfg->n_cvlans);
}
/* Get VLAN mode. */
if (cfg->vlan_mode) {
if (!strcmp(cfg->vlan_mode, "access")) {
s.vlan_mode = PORT_VLAN_ACCESS;
} else if (!strcmp(cfg->vlan_mode, "trunk")) {
s.vlan_mode = PORT_VLAN_TRUNK;
} else if (!strcmp(cfg->vlan_mode, "native-tagged")) {
s.vlan_mode = PORT_VLAN_NATIVE_TAGGED;
} else if (!strcmp(cfg->vlan_mode, "native-untagged")) {
s.vlan_mode = PORT_VLAN_NATIVE_UNTAGGED;
} else if (!strcmp(cfg->vlan_mode, "dot1q-tunnel")) {
s.vlan_mode = PORT_VLAN_DOT1Q_TUNNEL;
} else {
/* This "can't happen" because ovsdb-server should prevent it. */
VLOG_WARN("port %s: unknown VLAN mode %s, falling "
"back to trunk mode", port->name, cfg->vlan_mode);
s.vlan_mode = PORT_VLAN_TRUNK;
}
} else {
if (s.vlan >= 0) {
s.vlan_mode = PORT_VLAN_ACCESS;
if (cfg->n_trunks || cfg->n_cvlans) {
VLOG_WARN("port %s: ignoring trunks in favor of implicit vlan",
port->name);
}
} else {
s.vlan_mode = PORT_VLAN_TRUNK;
}
}
...
...
/* Register. */
ofproto_bundle_register(port->bridge->ofproto, port, &s);
}
最后在函数type_run中，将ofproto->bundles转换到struct xbundle中，并插入new_xcfg->xbundles。
static int
type_run(const char *type)
{
HMAP_FOR_EACH (ofproto, all_ofproto_dpifs_node, &all_ofproto_dpifs) {
HMAP_FOR_EACH (bundle, hmap_node, &ofproto->bundles) {
xlate_bundle_set(ofproto, bundle, bundle->name,
bundle->vlan_mode, bundle->qinq_ethtype,
bundle->vlan, bundle->trunks, bundle->cvlans,
bundle->use_priority_tags,
bundle->bond, bundle->lacp,
bundle->floodable, bundle->protected);
}
}
}
报文入方向vlan处理
网桥端口接收到报文后，如果快速路径查找不到相关流表，就会开始慢速路径的处理，最终会根据fdb表转发，调用xlate_normal。此函数中调用input_vid_is_valid根据入端口vlan模式配置，判断报文的去留。
//vid为报文携带的vlan id，如果报文不带vlan，则为0
//in_xbundle为报文入端口，其中包括端口上vlan相关的设置
static bool
input_vid_is_valid(const struct xlate_ctx *ctx,
uint16_t vid, struct xbundle *in_xbundle)
{
/* Allow any VID on the OFPP_NONE port. */
if (in_xbundle == &ofpp_none_bundle) {
return true;
}
switch (in_xbundle->vlan_mode) {
//access模式，如果报文带vlan，则drop
case PORT_VLAN_ACCESS:
if (vid) {
xlate_report_error(ctx, "dropping VLAN %"PRIu16" tagged "
"packet received on port %s configured as VLAN "
"%d access port", vid, in_xbundle->name,
in_xbundle->vlan);
return false;
}
return true;
//native tagged和native untagged模式下，如果报文不带vlan，则接收此报文。
//如果报文携带vlan，则就要判断此vlan是否在trunk vlan中。
//trunk vlan中会自动加入native vlan
case PORT_VLAN_NATIVE_UNTAGGED:
case PORT_VLAN_NATIVE_TAGGED:
if (!vid) {
/* Port must always carry its native VLAN. */
return true;
}
/* Fall through. */
//native tagged，native untagged和trunk模式都会走此流程，判断
//报文携带vlan是否在trunk vlan中
case PORT_VLAN_TRUNK:
if (!xbundle_trunks_vlan(in_xbundle, vid)) {
xlate_report_error(ctx, "dropping VLAN %"PRIu16" packet "
"received on port %s not configured for "
"trunking VLAN %"PRIu16,
vid, in_xbundle->name, vid);
return false;
}
return true;
case PORT_VLAN_DOT1Q_TUNNEL:
if (!xbundle_allows_cvlan(in_xbundle, vid)) {
xlate_report_error(ctx, "dropping VLAN %"PRIu16" packet received "
"on dot1q-tunnel port %s that excludes this "
"VLAN", vid, in_xbundle->name);
return false;
}
return true;
default:
OVS_NOT_REACHED();
}
}
如果报文通过了input_vid_is_valid的检查，则调用xvlan_input_translate获取vlan信息，以便报文使用此vlan信息在后续流程中进行转发。
//in_xbundle为入端口
//in_xvlan为报文携带的vlan，如果报文不带vlan，则为空
//xvlan输出参数
static void
xvlan_input_translate(const struct xbundle *in_xbundle,
const struct xvlan *in_xvlan, struct xvlan *xvlan)
{
switch (in_xbundle->vlan_mode) {
//access模式下，使用in_xbundle->vlan，此vlan为用户配置。
case PORT_VLAN_ACCESS:
memset(xvlan, 0, sizeof(*xvlan));
xvlan->v[0].tpid = in_xvlan->v[0].tpid ? in_xvlan->v[0].tpid :
ETH_TYPE_VLAN_8021Q;
xvlan->v[0].vid = in_xbundle->vlan;
xvlan->v[0].pcp = in_xvlan->v[0].pcp;
break;
//trunk模式下，使用in_xvlan即可
case PORT_VLAN_TRUNK:
xvlan_copy(xvlan, in_xvlan);
break;
//native_tagged和native_untagged模式下，也使用in_xvlan，
//如果in_xvlan为空，则说明报文不带vlan，使用native vlan
case PORT_VLAN_NATIVE_UNTAGGED:
case PORT_VLAN_NATIVE_TAGGED:
xvlan_copy(xvlan, in_xvlan);
if (!in_xvlan->v[0].vid) {
xvlan->v[0].tpid = in_xvlan->v[0].tpid ? in_xvlan->v[0].tpid :
ETH_TYPE_VLAN_8021Q;
xvlan->v[0].vid = in_xbundle->vlan;
xvlan->v[0].pcp = in_xvlan->v[0].pcp;
}
break;
case PORT_VLAN_DOT1Q_TUNNEL:
xvlan_copy(xvlan, in_xvlan);
xvlan_push_uninit(xvlan);
xvlan->v[0].tpid = in_xbundle->qinq_ethtype;
xvlan->v[0].vid = in_xbundle->vlan;
xvlan->v[0].pcp = 0;
break;
default:
OVS_NOT_REACHED();
}
}
报文出方向vlan处理
经过fdb表后，如果找到出端口，则调用output_normal将报文从出端口发出，如果没有找到出端口，则将报文发送到所有的端口，最终也会调用output_normal。此函数中调用xvlan_output_translate根据出端口vlan模式选择最终的vlan信息。
//out_xbundle出端口
//xvlan在xvlan_input_translate输出的vlan信息
//out_xvlan最终使用的vlan，报文会携带此vlan
static void
xvlan_output_translate(const struct xbundle *out_xbundle,
const struct xvlan *xvlan, struct xvlan *out_xvlan)
{
switch (out_xbundle->vlan_mode) {
//access模式，则设置out_xvlan为0，即报文发出去时不携带vlan
case PORT_VLAN_ACCESS:
memset(out_xvlan, 0, sizeof(*out_xvlan));
break;
//trunk和native_tagged模式下，报文发出去时携带vlan
case PORT_VLAN_TRUNK:
case PORT_VLAN_NATIVE_TAGGED:
xvlan_copy(out_xvlan, xvlan);
break;
//native_untagged模式下，如果报文out_xvlan中包含native vlan，
//则需要将此vlan去掉，即报文发出去时不携带vlan
case PORT_VLAN_NATIVE_UNTAGGED:
xvlan_copy(out_xvlan, xvlan);
if (xvlan->v[0].vid == out_xbundle->vlan) {
xvlan_pop(out_xvlan);
}
break;
case PORT_VLAN_DOT1Q_TUNNEL:
xvlan_copy(out_xvlan, xvlan);
xvlan_pop(out_xvlan);
break;
default:
OVS_NOT_REACHED();
}
}
配置
和vlan相关的配置有如下几个参数，每种vlan mode需要的参数不一样，下面分别实践。
vlan_mode 为 access时，只需要tag参数。
vlan_mode 为trunk时，只需要trunks参数。
vlan_mode为native−tagged或者native−untagged时，同时需要tag和trunks。
image.png
具体的命令如下
ovs-vsctl set port vetha tag=101
ovs-vsctl set port vetha vlan_mode=trunk
ovs-vsctl set port vetha trunks=101-102
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