Openvswitch原理与代码分析(6)：用户态流表flow table的操作

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Openvswitch原理与代码分析(6)：用户态流表flow table的操作

2024-08-14 12:55:56 218人阅读

当内核无法查找到流表项的时候，则会通过upcall来调用用户态ovs-vswtichd中的flow table。

会调用ofproto-dpif-upcall.c中的udpif_upcall_handler函数。

static void *
udpif_upcall_handler(void *arg)
{
????struct handler *handler = arg;
????struct udpif *udpif = handler->udpif;
?
????while (!latch_is_set(&handler->udpif->exit_latch)) {
????????if (recv_upcalls(handler)) {
????????????poll_immediate_wake();
????????} else {
????????????dpif_recv_wait(udpif->dpif, handler->handler_id);
????????????latch_wait(&udpif->exit_latch);
????????}
????????poll_block();
????}
?
????return NULL;
}

会调用static size_t recv_upcalls(struct handler *handler)

在这个函数里面

(1) 首先读取upcall调用static int upcall_receive(struct upcall *upcall, const struct dpif_backer *backer, const struct dp_packet *packet, enum dpif_upcall_type type, const struct nlattr *userdata, const struct flow *flow, const unsigned int mru, const ovs_u128 *ufid, const unsigned pmd_id)

(2) 其次提取包头调用void flow_extract(struct dp_packet *packet, struct flow *flow)，提取出的flow如下：

struct flow {
????/* Metadata */
????struct flow_tnl tunnel; /* Encapsulating tunnel parameters. */
????ovs_be64 metadata; /* OpenFlow Metadata. */
????uint32_t regs[FLOW_N_REGS]; /* Registers. */
????uint32_t skb_priority; /* Packet priority for QoS. */
????uint32_t pkt_mark; /* Packet mark. */
????uint32_t dp_hash; /* Datapath computed hash value. The exact
?????????????????????????????????* computation is opaque to the user space. */
????union flow_in_port in_port; /* Input port.*/
????uint32_t recirc_id; /* Must be exact match. */
????uint16_t ct_state; /* Connection tracking state. */
????uint16_t ct_zone; /* Connection tracking zone. */
????uint32_t ct_mark; /* Connection mark.*/
????uint8_t pad1[4]; /* Pad to 64 bits. */
????ovs_u128 ct_label; /* Connection label. */
????uint32_t conj_id; /* Conjunction ID. */
????ofp_port_t actset_output; /* Output port in action set. */
????uint8_t pad2[2]; /* Pad to 64 bits. */
?
????/* L2, Order the same as in the Ethernet header! (64-bit aligned) */
????struct eth_addr dl_dst; /* Ethernet destination address. */
????struct eth_addr dl_src; /* Ethernet source address. */
????ovs_be16 dl_type; /* Ethernet frame type. */
????ovs_be16 vlan_tci; /* If 802.1Q, TCI | VLAN_CFI; otherwise 0. */
????ovs_be32 mpls_lse[ROUND_UP(FLOW_MAX_MPLS_LABELS, 2)]; /* MPLS label stack
?????????????????????????????????????????????????????????????(with padding). */
????/* L3 (64-bit aligned) */
????ovs_be32 nw_src; /* IPv4 source address. */
????ovs_be32 nw_dst; /* IPv4 destination address. */
????struct in6_addr ipv6_src; /* IPv6 source address. */
????struct in6_addr ipv6_dst; /* IPv6 destination address. */
????ovs_be32 ipv6_label; /* IPv6 flow label. */
????uint8_t nw_frag; /* FLOW_FRAG_* flags. */
????uint8_t nw_tos; /* IP ToS (including DSCP and ECN). */
????uint8_t nw_ttl; /* IP TTL/Hop Limit. */
????uint8_t nw_proto; /* IP protocol or low 8 bits of ARP opcode. */
????struct in6_addr nd_target; /* IPv6 neighbor discovery (ND) target. */
????struct eth_addr arp_sha; /* ARP/ND source hardware address. */
????struct eth_addr arp_tha; /* ARP/ND target hardware address. */
????ovs_be16 tcp_flags; /* TCP flags. With L3 to avoid matching L4. */
????ovs_be16 pad3; /* Pad to 64 bits. */
?
????/* L4 (64-bit aligned) */
????ovs_be16 tp_src; /* TCP/UDP/SCTP source port/ICMP type. */
????ovs_be16 tp_dst; /* TCP/UDP/SCTP destination port/ICMP code. */
????ovs_be32 igmp_group_ip4; /* IGMP group IPv4 address.
?????????????????????????????????* Keep last for BUILD_ASSERT_DECL below. */
};

(3) 然后调用static int process_upcall(struct udpif *udpif, struct upcall *upcall, struct ofpbuf *odp_actions, struct flow_wildcards *wc)来处理upcall。

对于MISS_UPCALL，调用static void upcall_xlate(struct udpif *udpif, struct upcall *upcall, struct ofpbuf *odp_actions, struct flow_wildcards *wc)

switch (classify_upcall(upcall->type, userdata)) {
case MISS_UPCALL:
????upcall_xlate(udpif, upcall, odp_actions, wc);
????return 0;

会调用enum xlate_error xlate_actions(struct xlate_in *xin, struct xlate_out *xout)

在这个函数里面，会在flow table里面查找rule

ctx.rule = rule_dpif_lookup_from_table( ctx.xbridge->ofproto, ctx.tables_version, flow, xin->wc, ctx.xin->resubmit_stats, &ctx.table_id, flow->in_port.ofp_port, true, true);

找到rule之后，调用static void do_xlate_actions(const struct ofpact *ofpacts, size_t ofpacts_len, struct xlate_ctx *ctx)在这个函数里面，根据action的不同，修改flow的内容。

switch (a->type) {
case OFPACT_OUTPUT:
????xlate_output_action(ctx, ofpact_get_OUTPUT(a)->port,
????????????????????????ofpact_get_OUTPUT(a)->max_len, true);
????break;
?
case OFPACT_SET_VLAN_VID:
????wc->masks.vlan_tci |= htons(VLAN_VID_MASK | VLAN_CFI);
????if (flow->vlan_tci & htons(VLAN_CFI) ||
????????ofpact_get_SET_VLAN_VID(a)->push_vlan_if_needed) {
????????flow->vlan_tci &= ~htons(VLAN_VID_MASK);
????????flow->vlan_tci |= (htons(ofpact_get_SET_VLAN_VID(a)->vlan_vid)
???????????????????????????| htons(VLAN_CFI));
????}
????break;
?
case OFPACT_SET_ETH_SRC:
????WC_MASK_FIELD(wc, dl_src);
????flow->dl_src = http://www.mamicode.com/ofpact_get_SET_ETH_SRC(a)->mac;>
????break;
?
case OFPACT_SET_ETH_DST:
????WC_MASK_FIELD(wc, dl_dst);
????flow->dl_dst = ofpact_get_SET_ETH_DST(a)->mac;
????break;
?
case OFPACT_SET_IPV4_SRC:
????CHECK_MPLS_RECIRCULATION();
????if (flow->dl_type == htons(ETH_TYPE_IP)) {
????????memset(&wc->masks.nw_src, 0xff, sizeof wc->masks.nw_src);
????????flow->nw_src = http://www.mamicode.com/ofpact_get_SET_IPV4_SRC(a)->ipv4;>
????}
????break;
?
case OFPACT_SET_IPV4_DST:
????CHECK_MPLS_RECIRCULATION();
????if (flow->dl_type == htons(ETH_TYPE_IP)) {
????????memset(&wc->masks.nw_dst, 0xff, sizeof wc->masks.nw_dst);
????????flow->nw_dst = ofpact_get_SET_IPV4_DST(a)->ipv4;
????}
????break;
?
case OFPACT_SET_L4_SRC_PORT:
????CHECK_MPLS_RECIRCULATION();
????if (is_ip_any(flow) && !(flow->nw_frag & FLOW_NW_FRAG_LATER)) {
????????memset(&wc->masks.nw_proto, 0xff, sizeof wc->masks.nw_proto);
????????memset(&wc->masks.tp_src, 0xff, sizeof wc->masks.tp_src);
????????flow->tp_src = http://www.mamicode.com/htons(ofpact_get_SET_L4_SRC_PORT(a)->port);>
????}
????break;
?
case OFPACT_SET_L4_DST_PORT:
????CHECK_MPLS_RECIRCULATION();
????if (is_ip_any(flow) && !(flow->nw_frag & FLOW_NW_FRAG_LATER)) {
????????memset(&wc->masks.nw_proto, 0xff, sizeof wc->masks.nw_proto);
????????memset(&wc->masks.tp_dst, 0xff, sizeof wc->masks.tp_dst);
????????flow->tp_dst = htons(ofpact_get_SET_L4_DST_PORT(a)->port);
????}
????break;

(4) 最后调用static void handle_upcalls(struct udpif *udpif, struct upcall *upcalls, size_t n_upcalls)将flow rule添加到内核中的datapath

他会调用void dpif_operate(struct dpif *dpif, struct dpif_op **ops, size_t n_ops)，他会调用dpif->dpif_class->operate(dpif, ops, chunk);

会调用dpif_netlink_operate()

static void
dpif_netlink_operate(struct dpif *dpif_, struct dpif_op **ops, size_t n_ops)
{
????struct dpif_netlink *dpif = dpif_netlink_cast(dpif_);
?
????while (n_ops > 0) {
????????size_t chunk = dpif_netlink_operate__(dpif, ops, n_ops);
????????ops += chunk;
????????n_ops -= chunk;
????}
}

在static size_t dpif_netlink_operate__(struct dpif_netlink *dpif, struct dpif_op **ops, size_t n_ops)中，有以下的代码：

switch (op->type) {
case DPIF_OP_FLOW_PUT:
????put = &op->u.flow_put;
????dpif_netlink_init_flow_put(dpif, put, &flow);
????if (put->stats) {
????????flow.nlmsg_flags |= NLM_F_ECHO;
????????aux->txn.reply = &aux->reply;
????}
????dpif_netlink_flow_to_ofpbuf(&flow, &aux->request);
????break;
?
case DPIF_OP_FLOW_DEL:
????del = &op->u.flow_del;
????dpif_netlink_init_flow_del(dpif, del, &flow);
????if (del->stats) {
????????flow.nlmsg_flags |= NLM_F_ECHO;
????????aux->txn.reply = &aux->reply;
????}
????dpif_netlink_flow_to_ofpbuf(&flow, &aux->request);
????break;

会调用netlink修改内核中datapath的规则。

Openvswitch原理与代码分析(6)：用户态流表flow table的操作

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首页 > 代码库 > Openvswitch原理与代码分析(6)：用户态流表flow table的操作

Openvswitch原理与代码分析(6)：用户态流表flow table的操作

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