On Tue, Feb 16, 2021 at 4:21 AM Han Zhou <[email protected]> wrote: > > > On Wed, Feb 10, 2021 at 2:17 PM Lorenzo Bianconi < > [email protected]> wrote: > > > > Increase priority for automatic routes (routes created assigning IP > > addresses to OVN logical router interfaces) in order to always prefer > them > > over static routes since the router has a direct link to the destination > > address (possible use-case can be found here [0]). > > > > [0] https://bugzilla.redhat.com/show_bug.cgi?id=1891516 > > > > Hi Lorenzo, Tim, > > While the patch may solve the problem in the bug report, I think there is > something more fundamental to be discussed. The problem is caused by > ovn-k8s's use of "src-ip" in static routes which overrides the > direct-connected route. I think the implementation of "src-ip" support in > the static route is somehow flawed. The priorities of the flows generated > by static routes are calculated according to the prefix length, so that > longest prefix routes are prioritised when there are multiple route > matches, which is correct when comparing matches among "dst-ip" routes or > among "src-ip" routes, but is not correct between "dst-ip" and "src-ip" > routes. Comparison of prefix length between these two types of static > routes doesn't make sense, because they match by different fields (src-ip > v.s. dst-ip). For example, when there are static routes: > 1. 192.168.0.0/24 via 100.64.0.1 src-ip > 2. 10.0.0.0/20 via 100.64.0.2 dst-ip > > In this example, a packet from 192.168.0.1 to 10.0.0.1 matches both > routes, but it is unreasonable to say it should follow the 1st route just > because it has longer prefix length. Instead, we should prioritize one type > over the other. It seems in physical router implementation policy based > routing always has higher priority than destination routing, so we should > probably enforce it in a similar way in OVN, i.e. set "src-ip" flows with > higher priority than all the "dst-ip" flows. In fact, the policy routing > table already supported this behavior because it is examined before the > static route table. > > Since the "src-ip" feature in the static route table is flawed, and can be > replaced by the policy routing table, I'd suggest to deprecate it. For > correctness, users (like ovn-k8s) should use the policy routing table > instead for the src-ip based routing rules. Users have full control of how > they want the packets to be routed. For the use case mentioned in the bug > report, it should have two rules in the policy routing table: >
> 100 ip.dst == 100.64.0.0/16 accept # for directly connected destination, > skip the src-ip rules > 90 ip.src == 10.244.0.0/24 nexthop 100.64.0.1 # src-ip rules > > Would this better satisfy the need of ovn-k8s? > I believe this is correct. src-ip matching should be done in the policy table so traditional dest based routing is handled in default routing table. Need to go double check though. > If the above is agreed, the priority change of directly connected routes > from this patch is irrelevant to the problem reported in the bug, because > policy routing rules are examined before the static routing table anyway, > so no matter how high the route priority is, it wouldn't matter. In > addition, it seems to me no real use cases would benefit from this change, > but I could be wrong and please correct me if so. > > I disagree with this. Trying to override a directly connected route is fundamentally wrong, which is why real routers specifically stop a user from being able to do this. What if a user who had a router attached to 100.64.0.0/16, adds a /32 route for 100.64.0.1 via another interface/subnet? That would take precedence over the directly attached route in OVN iiuc and pretty much guarantee improper networking. Directly connected routes should always take precedence, and therefore the default route lflows that get installed should always have the highest possible priority. > Thanks, > Han > > > Signed-off-by: Lorenzo Bianconi <[email protected]> > > --- > > northd/ovn-northd.c | 27 ++++++++++++++++----------- > > 1 file changed, 16 insertions(+), 11 deletions(-) > > > > diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c > > index b2b5f6a1b..dc8706f2f 100644 > > --- a/northd/ovn-northd.c > > +++ b/northd/ovn-northd.c > > @@ -7994,18 +7994,23 @@ build_route_prefix_s(const struct in6_addr > *prefix, unsigned int plen) > > > > static void > > build_route_match(const struct ovn_port *op_inport, const char > *network_s, > > - int plen, bool is_src_route, bool is_ipv4, struct ds > *match, > > - uint16_t *priority) > > + int plen, bool is_src_route, bool is_ipv4, bool > automatic, > > + struct ds *match, uint16_t *priority) > > { > > + int prefix_len = plen; > > const char *dir; > > /* The priority here is calculated to implement longest-prefix-match > > - * routing. */ > > + * routing. Automatic routes have max priority */ > > + if (automatic) { > > + prefix_len = is_ipv4 ? 32 : 128; > > + prefix_len++; > > + } > > if (is_src_route) { > > dir = "src"; > > - *priority = plen * 2; > > + *priority = prefix_len * 2; > > } else { > > dir = "dst"; > > - *priority = (plen * 2) + 1; > > + *priority = (prefix_len * 2) + 1; > > } > > > > if (op_inport) { > > @@ -8172,7 +8177,7 @@ build_ecmp_route_flow(struct hmap *lflows, struct > ovn_datapath *od, > > > > char *prefix_s = build_route_prefix_s(&eg->prefix, eg->plen); > > build_route_match(NULL, prefix_s, eg->plen, eg->is_src_route, > is_ipv4, > > - &route_match, &priority); > > + false, &route_match, &priority); > > free(prefix_s); > > > > struct ds actions = DS_EMPTY_INITIALIZER; > > @@ -8246,7 +8251,7 @@ build_ecmp_route_flow(struct hmap *lflows, struct > ovn_datapath *od, > > static void > > add_route(struct hmap *lflows, const struct ovn_port *op, > > const char *lrp_addr_s, const char *network_s, int plen, > > - const char *gateway, bool is_src_route, > > + const char *gateway, bool is_src_route, bool automatic, > > const struct ovsdb_idl_row *stage_hint) > > { > > bool is_ipv4 = strchr(network_s, '.') ? true : false; > > @@ -8263,7 +8268,7 @@ add_route(struct hmap *lflows, const struct > ovn_port *op, > > } > > } > > build_route_match(op_inport, network_s, plen, is_src_route, is_ipv4, > > - &match, &priority); > > + automatic, &match, &priority); > > > > struct ds common_actions = DS_EMPTY_INITIALIZER; > > ds_put_format(&common_actions, REG_ECMP_GROUP_ID" = 0; %s = ", > > @@ -8319,7 +8324,7 @@ build_static_route_flow(struct hmap *lflows, > struct ovn_datapath *od, > > > > char *prefix_s = build_route_prefix_s(&route_->prefix, > route_->plen); > > add_route(lflows, out_port, lrp_addr_s, prefix_s, route_->plen, > > - route->nexthop, route_->is_src_route, > > + route->nexthop, route_->is_src_route, false, > > &route->header_); > > > > free(prefix_s); > > @@ -9389,14 +9394,14 @@ build_ip_routing_flows_for_lrouter_port( > > add_route(lflows, op, op->lrp_networks.ipv4_addrs[i].addr_s, > > op->lrp_networks.ipv4_addrs[i].network_s, > > op->lrp_networks.ipv4_addrs[i].plen, NULL, false, > > - &op->nbrp->header_); > > + true, &op->nbrp->header_); > > } > > > > for (int i = 0; i < op->lrp_networks.n_ipv6_addrs; i++) { > > add_route(lflows, op, op->lrp_networks.ipv6_addrs[i].addr_s, > > op->lrp_networks.ipv6_addrs[i].network_s, > > op->lrp_networks.ipv6_addrs[i].plen, NULL, false, > > - &op->nbrp->header_); > > + true, &op->nbrp->header_); > > } > > } > > } > > -- > > 2.29.2 > > > > _______________________________________________ > > dev mailing list > > [email protected] > > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
