[ovs-dev] [PATCH v3 ovn 1/4] ovn-northd: Drop IP packets destined to router owned IPs (after NAT).

Han Zhou hzhou at ovn.org
Mon Sep 21 06:37:59 UTC 2020


On Thu, Sep 17, 2020 at 5:51 AM Dumitru Ceara <dceara at redhat.com> wrote:
>
> OVN was dropping IP packets destined to IPs owned by logical routers but
> only if those IPs are not used for SNAT rules. However, if a packet
> doesn't match an existing NAT session and its destination is still a
> router owned IP, it can be safely dropped. Otherwise it will trigger an
> unnecessary packet-in in stage lr_in_arp_request.
>
> To achieve that we add flows that drop traffic to router owned SNAT IPs in
> table lr_in_arp_resolve.
>
> Reported-by: Tim Rozet <trozet at redhat.com>
> Reported-at: https://bugzilla.redhat.com/1876174
> Signed-off-by: Dumitru Ceara <dceara at redhat.com>
> ---
>  northd/ovn-northd.8.xml |   24 ++++++
>  northd/ovn-northd.c     |  194
+++++++++++++++++++++++++++--------------------
>  tests/ovn.at            |   88 +++++++++++++++++++++
>  3 files changed, 225 insertions(+), 81 deletions(-)
>
> diff --git a/northd/ovn-northd.8.xml b/northd/ovn-northd.8.xml
> index bd42105..f1c7c9b 100644
> --- a/northd/ovn-northd.8.xml
> +++ b/northd/ovn-northd.8.xml
> @@ -3089,6 +3089,30 @@ outport = <var>P</var>;
>
>        <li>
>          <p>
> +          Traffic with IP destination an address owned by the router
should be
> +          dropped. Such traffic is normally dropped in ingress table
> +          <code>IP Input</code> except for IPs that are also shared with
SNAT
> +          rules. However, if there was no unSNAT operation that happened
> +          successfully until this point in the pipeline and the
destination IP
> +          of the packet is still a router owned IP, the packets can be
safely
> +          dropped.
> +        </p>
> +
> +        <p>
> +          A priority-1 logical flow with match <code>ip4.dst =
{..}</code>
> +          matches on traffic destined to router owned IPv4 addresses
which are
> +          also SNAT IPs. This flow has action <code>drop;</code>.
> +        </p>
> +
> +        <p>
> +          A priority-1 logical flow with match <code>ip6.dst =
{..}</code>
> +          matches on traffic destined to router owned IPv6 addresses
which are
> +          also SNAT IPs. This flow has action <code>drop;</code>.
> +        </p>
> +      </li>
> +
> +      <li>
> +        <p>
>            Dynamic MAC bindings.  These flows resolve MAC-to-IP bindings
>            that have become known dynamically through ARP or neighbor
>            discovery.  (The ingress table <code>ARP Request</code> will
> diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
> index cfec6a2..d5d7631 100644
> --- a/northd/ovn-northd.c
> +++ b/northd/ovn-northd.c
> @@ -623,6 +623,9 @@ struct ovn_datapath {
>      /* NAT entries configured on the router. */
>      struct ovn_nat *nat_entries;
>
> +    /* SNAT IPs used by the router. */
> +    struct sset snat_ips;
> +
>      struct ovn_port **localnet_ports;
>      size_t n_localnet_ports;
>
> @@ -641,6 +644,10 @@ struct ovn_nat {
>      struct lport_addresses ext_addrs;
>  };
>
> +static bool
> +get_force_snat_ip(struct ovn_datapath *od, const char *key_type,
> +                  struct lport_addresses *laddrs);
> +
>  /* Returns true if a 'nat_entry' is valid, i.e.:
>   * - parsing was successful.
>   * - the string yielded exactly one IPv4 address or exactly one IPv6
address.
> @@ -663,7 +670,35 @@ nat_entry_is_v6(const struct ovn_nat *nat_entry)
>  static void
>  init_nat_entries(struct ovn_datapath *od)
>  {
> -    if (!od->nbr || od->nbr->n_nat == 0) {
> +    struct lport_addresses snat_addrs;
> +
> +    if (!od->nbr) {
> +        return;
> +    }
> +
> +    sset_init(&od->snat_ips);
> +    if (get_force_snat_ip(od, "dnat", &snat_addrs)) {
> +        if (snat_addrs.n_ipv4_addrs) {
> +            sset_add(&od->snat_ips, snat_addrs.ipv4_addrs[0].addr_s);
> +        }
> +        if (snat_addrs.n_ipv6_addrs) {
> +            sset_add(&od->snat_ips, snat_addrs.ipv6_addrs[0].addr_s);
> +        }
> +        destroy_lport_addresses(&snat_addrs);
> +    }
> +
> +    memset(&snat_addrs, 0, sizeof(snat_addrs));
> +    if (get_force_snat_ip(od, "lb", &snat_addrs)) {
> +        if (snat_addrs.n_ipv4_addrs) {
> +            sset_add(&od->snat_ips, snat_addrs.ipv4_addrs[0].addr_s);
> +        }
> +        if (snat_addrs.n_ipv6_addrs) {
> +            sset_add(&od->snat_ips, snat_addrs.ipv6_addrs[0].addr_s);
> +        }
> +        destroy_lport_addresses(&snat_addrs);
> +    }
> +
> +    if (!od->nbr->n_nat) {
>          return;
>      }
>
> @@ -682,6 +717,13 @@ init_nat_entries(struct ovn_datapath *od)
>              VLOG_WARN_RL(&rl,
>                           "Bad ip address %s in nat configuration "
>                           "for router %s", nat->external_ip,
od->nbr->name);
> +            continue;
> +        }
> +
> +        if (!nat_entry_is_v6(nat_entry)) {
> +            sset_add(&od->snat_ips,
nat_entry->ext_addrs.ipv4_addrs[0].addr_s);
> +        } else {
> +            sset_add(&od->snat_ips,
nat_entry->ext_addrs.ipv6_addrs[0].addr_s);
>          }
>      }
>  }
> @@ -693,6 +735,7 @@ destroy_nat_entries(struct ovn_datapath *od)
>          return;
>      }
>
> +    sset_destroy(&od->snat_ips);
>      for (size_t i = 0; i < od->nbr->n_nat; i++) {
>          destroy_lport_addresses(&od->nat_entries[i].ext_addrs);
>      }
> @@ -8744,6 +8787,68 @@ build_lrouter_flows(struct hmap *datapaths, struct
hmap *ports,
>                  op, lflows, &match, &actions);
>      }
>
> +    /* Drop IP traffic destined to router owned IPs. Part of it is
dropped
> +     * in stage "lr_in_ip_input" but traffic that could have been
unSNATed
> +     * but didn't match any existing session might still end up here.
> +     */
> +    HMAP_FOR_EACH (op, key_node, ports) {
> +        if (!op->nbrp) {
> +            continue;
> +        }
> +
> +        if (op->lrp_networks.n_ipv4_addrs) {
> +            ds_clear(&match);
> +            for (size_t i = 0; i < op->lrp_networks.n_ipv4_addrs; i++) {
> +                if (!sset_find(&op->od->snat_ips,
> +                               op->lrp_networks.ipv4_addrs[i].addr_s)) {
> +                    continue;
> +                }
> +                ds_put_format(&match, "%s, ",
> +                              op->lrp_networks.ipv4_addrs[i].addr_s);
> +            }
> +
> +            if (ds_last(&match) != EOF) {
> +                ds_chomp(&match, ' ');
> +                ds_chomp(&match, ',');
> +
> +                char *drop_match = xasprintf("ip4.dst == {%s}",
> +                                             ds_cstr(&match));
> +                /* Drop traffic with IP.dest == router-ip. */
> +                ovn_lflow_add_with_hint(lflows, op->od,
> +                                        S_ROUTER_IN_ARP_RESOLVE, 1,
> +                                        drop_match, "drop;",
> +                                        &op->nbrp->header_);
> +                free(drop_match);
> +            }
> +        }
> +
> +        if (op->lrp_networks.n_ipv6_addrs) {
> +            ds_clear(&match);
> +            for (size_t i = 0; i < op->lrp_networks.n_ipv6_addrs; i++) {
> +                if (!sset_find(&op->od->snat_ips,
> +                               op->lrp_networks.ipv6_addrs[i].addr_s)) {
> +                    continue;
> +                }
> +                ds_put_format(&match, "%s, ",
> +                              op->lrp_networks.ipv6_addrs[i].addr_s);
> +            }
> +
> +            if (ds_last(&match) != EOF) {
> +                ds_chomp(&match, ' ');
> +                ds_chomp(&match, ',');
> +
> +                char *drop_match = xasprintf("ip6.dst == {%s}",
> +                                             ds_cstr(&match));
> +                /* Drop traffic with IP.dest == router-ip. */
> +                ovn_lflow_add_with_hint(lflows, op->od,
> +                                        S_ROUTER_IN_ARP_RESOLVE, 1,
> +                                        drop_match, "drop;",
> +                                        &op->nbrp->header_);
> +                free(drop_match);
> +            }
> +        }
> +    }
> +
>      HMAP_FOR_EACH (od, key_node, datapaths) {
>          if (!od->nbr) {
>              continue;
> @@ -9035,77 +9140,15 @@ build_lrouter_flows(struct hmap *datapaths,
struct hmap *ports,
>          }
>
>          /* A gateway router can have 4 SNAT IP addresses to force DNATed
and
> -         * LBed traffic respectively to be SNATed.  In addition, there
can be
> -         * a number of SNAT rules in the NAT table. */
> -        struct v46_ip *snat_ips = xmalloc(sizeof *snat_ips
> -                                          * (op->od->nbr->n_nat + 4));
> -        size_t n_snat_ips = 0;
> -        struct lport_addresses snat_addrs;
> -
> -        if (get_force_snat_ip(op->od, "dnat", &snat_addrs)) {
> -            if (snat_addrs.n_ipv4_addrs) {
> -                snat_ips[n_snat_ips].family = AF_INET;
> -                snat_ips[n_snat_ips++].ipv4 =
snat_addrs.ipv4_addrs[0].addr;
> -            }
> -            if (snat_addrs.n_ipv6_addrs) {
> -                snat_ips[n_snat_ips].family = AF_INET6;
> -                snat_ips[n_snat_ips++].ipv6 =
snat_addrs.ipv6_addrs[0].addr;
> -            }
> -            destroy_lport_addresses(&snat_addrs);
> -        }
> -
> -        memset(&snat_addrs, 0, sizeof(snat_addrs));
> -        if (get_force_snat_ip(op->od, "lb", &snat_addrs)) {
> -            if (snat_addrs.n_ipv4_addrs) {
> -                snat_ips[n_snat_ips].family = AF_INET;
> -                snat_ips[n_snat_ips++].ipv4 =
snat_addrs.ipv4_addrs[0].addr;
> -            }
> -            if (snat_addrs.n_ipv6_addrs) {
> -                snat_ips[n_snat_ips].family = AF_INET6;
> -                snat_ips[n_snat_ips++].ipv6 =
snat_addrs.ipv6_addrs[0].addr;
> -            }
> -            destroy_lport_addresses(&snat_addrs);
> -        }
> -
> -        for (size_t i = 0; i < op->od->nbr->n_nat; i++) {
> -            struct ovn_nat *nat_entry = &op->od->nat_entries[i];
> -            const struct nbrec_nat *nat = nat_entry->nb;
> -
> -            /* Skip entries we failed to parse. */
> -            if (!nat_entry_is_valid(nat_entry)) {
> -                continue;
> -            }
> -
> -            if (!strcmp(nat->type, "snat")) {
> -                if (nat_entry_is_v6(nat_entry)) {
> -                    struct in6_addr *ipv6 =
> -                        &nat_entry->ext_addrs.ipv6_addrs[0].addr;
> -
> -                    snat_ips[n_snat_ips].family = AF_INET6;
> -                    snat_ips[n_snat_ips++].ipv6 = *ipv6;
> -                } else {
> -                    ovs_be32 ip =
nat_entry->ext_addrs.ipv4_addrs[0].addr;
> -                    snat_ips[n_snat_ips].family = AF_INET;
> -                    snat_ips[n_snat_ips++].ipv4 = ip;
> -                }
> -            }
> -        }
> -
> +         * LBed traffic respectively to be SNATed. In addition, there
can be
> +         * a number of SNAT rules in the NAT table.
> +         * Skip all of them for drop flows. */
>          ds_clear(&match);
>          ds_put_cstr(&match, "ip4.dst == {");
>          bool has_drop_ips = false;
>          for (int i = 0; i < op->lrp_networks.n_ipv4_addrs; i++) {
> -            bool snat_ip_is_router_ip = false;
> -            for (int j = 0; j < n_snat_ips; j++) {
> -                /* Packets to SNAT IPs should not be dropped. */
> -                if (snat_ips[j].family == AF_INET
> -                    && op->lrp_networks.ipv4_addrs[i].addr
> -                       == snat_ips[j].ipv4) {
> -                        snat_ip_is_router_ip = true;
> -                        break;
> -                }
> -            }
> -            if (snat_ip_is_router_ip) {
> +            if (sset_find(&op->od->snat_ips,
> +                          op->lrp_networks.ipv4_addrs[i].addr_s)) {
>                  continue;
>              }
>              ds_put_format(&match, "%s, ",
> @@ -9122,17 +9165,8 @@ build_lrouter_flows(struct hmap *datapaths, struct
hmap *ports,
>          }
>
>          for (int i = 0; i < op->lrp_networks.n_ipv6_addrs; i++) {
> -            bool snat_ip_is_router_ip = false;
> -            for (int j = 0; j < n_snat_ips; j++) {
> -                /* Packets to SNAT IPs should not be dropped. */
> -                if (snat_ips[j].family == AF_INET6
> -                    && !memcmp(&op->lrp_networks.ipv6_addrs[i].addr,
> -                               &snat_ips[j].ipv6, sizeof
snat_ips[j].ipv6)) {
> -                    snat_ip_is_router_ip = true;
> -                    break;
> -                }
> -            }
> -            if (snat_ip_is_router_ip) {
> +            if (sset_find(&op->od->snat_ips,
> +                          op->lrp_networks.ipv6_addrs[i].addr_s)) {
>                  continue;
>              }
>              ds_put_format(&match, "%s, ",
> @@ -9151,8 +9185,6 @@ build_lrouter_flows(struct hmap *datapaths, struct
hmap *ports,
>                                      &op->nbrp->header_);
>          }
>
> -        free(snat_ips);
> -
>          /* ARP/NS packets are taken care of per router. The only
exception
>           * is on the l3dgw_port where we might need to use a different
>           * ETH address.
> diff --git a/tests/ovn.at b/tests/ovn.at
> index a6f1fb5..cb7e7cc 100644
> --- a/tests/ovn.at
> +++ b/tests/ovn.at
> @@ -21659,6 +21659,94 @@ OVS_WAIT_UNTIL([test x$(as hv1 ovn-appctl -t
ovn-controller debug/status) = "xru
>  OVN_CLEANUP([hv1])
>  AT_CLEANUP
>
> +# Test dropping traffic destined to router owned IPs.
> +AT_SETUP([ovn -- gateway router drop traffic for own IPs])
> +ovn_start
> +
> +ovn-nbctl lr-add r1 -- set logical_router r1 options:chassis=hv1
> +ovn-nbctl ls-add s1
> +
> +# Connnect r1 to s1.
> +ovn-nbctl lrp-add r1 lrp-r1-s1 00:00:00:00:01:01 10.0.1.1/24
> +ovn-nbctl lsp-add s1 lsp-s1-r1 -- set Logical_Switch_Port lsp-s1-r1
type=router \
> +    options:router-port=lrp-r1-s1 addresses=router
> +
> +# Create logical port p1 in s1
> +ovn-nbctl lsp-add s1 p1 \
> +-- lsp-set-addresses p1 "f0:00:00:00:01:02 10.0.1.2"
> +
> +# Create two hypervisor and create OVS ports corresponding to logical
ports.
> +net_add n1
> +
> +sim_add hv1
> +as hv1
> +ovs-vsctl add-br br-phys
> +ovn_attach n1 br-phys 192.168.0.1
> +ovs-vsctl -- add-port br-int hv1-vif1 -- \
> +    set interface hv1-vif1 external-ids:iface-id=p1 \
> +    options:tx_pcap=hv1/vif1-tx.pcap \
> +    options:rxq_pcap=hv1/vif1-rx.pcap \
> +    ofport-request=1
> +
> +# Pre-populate the hypervisors' ARP tables so that we don't lose any
> +# packets for ARP resolution (native tunneling doesn't queue packets
> +# for ARP resolution).
> +OVN_POPULATE_ARP
> +
> +ovn-nbctl --wait=hv sync
> +
> +sw_key=$(ovn-sbctl --bare --columns tunnel_key list datapath_binding r1)
> +
> +AT_CHECK([ovn-sbctl lflow-list | grep lr_in_arp_resolve | grep
10.0.1.1], [1], [])
> +
> +ip_to_hex() {
> +    printf "%02x%02x%02x%02x" "$@"
> +}
> +
> +# Send ip packets from p1 to lrp-r1-s1
> +src_mac="f00000000102"
> +dst_mac="000000000101"
> +src_ip=`ip_to_hex 10 0 1 2`
> +dst_ip=`ip_to_hex 10 0 1 1`
>
+packet=${dst_mac}${src_mac}08004500001c0000000040110000${src_ip}${dst_ip}0035111100080000
> +as hv1 ovs-appctl netdev-dummy/receive hv1-vif1 $packet
> +
> +# No packet-ins should reach ovn-controller.
> +AT_CHECK([as hv1 ovs-ofctl dump-flows br-int | grep "actions=controller"
| grep -v n_packets=0 -c], [1], [dnl
> +0
> +])
> +
> +# The packet should have been dropped in the lr_in_ip_input stage.
> +AT_CHECK([as hv1 ovs-ofctl dump-flows br-int | grep -E "table=11,
n_packets=1,.* priority=60,ip,metadata=0x${sw_key},nw_dst=10.0.1.1
actions=drop" -c], [0], [dnl
> +1
> +])
> +
> +# Use the router IP as SNAT IP.
> +ovn-nbctl set logical_router r1 options:lb_force_snat_ip=10.0.1.1
> +ovn-nbctl --wait=hv sync
> +
> +# Send ip packets from p1 to lrp-r1-s1
> +src_mac="f00000000102"
> +dst_mac="000000000101"
> +src_ip=`ip_to_hex 10 0 1 2`
> +dst_ip=`ip_to_hex 10 0 1 1`
>
+packet=${dst_mac}${src_mac}08004500001c0000000040110000${src_ip}${dst_ip}0035111100080000
> +as hv1 ovs-appctl netdev-dummy/receive hv1-vif1 $packet
> +
> +# Even after configuring a router owned IP for SNAT, no packet-ins should
> +# reach ovn-controller.
> +AT_CHECK([as hv1 ovs-ofctl dump-flows br-int | grep "actions=controller"
| grep -v n_packets=0 -c], [1], [dnl
> +0
> +])
> +
> +# The packet should've been dropped in the lr_in_arp_resolve stage.
> +AT_CHECK([as hv1 ovs-ofctl dump-flows br-int | grep -E "table=21,
n_packets=1,.* priority=1,ip,metadata=0x${sw_key},nw_dst=10.0.1.1
actions=drop" -c], [0], [dnl
> +1
> +])
> +
> +OVN_CLEANUP([hv1])
> +AT_CLEANUP
> +
>  AT_SETUP([ovn -- nb_cfg timestamp])
>  ovn_start
>
>
> _______________________________________________
> dev mailing list
> dev at openvswitch.org
> https://mail.openvswitch.org/mailman/listinfo/ovs-dev

Acked-by: Han Zhou <hzhou at ovn.org>


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