[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
>
>
> _______________________________________________
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> dev at openvswitch.org
> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
Acked-by: Han Zhou <hzhou at ovn.org>
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