On Fri, Jul 01, 2016 at 03:23:39AM -0700, Gurucharan Shetty wrote:
> OVN currently supports multiple gateway routers (residing on
> different chassis) connected to the same logical topology.
>
> When external traffic enters the logical topology, they can enter
> from any gateway routers and reach its eventual destination. This
> is achieved with proper static routes configured on the gateway
> routers.
>
> But when traffic is initiated in the logical space by a logical
> port, we do not have a good way to distribute that traffic across
> multiple gateway routers.
>
> This commit introduces one particular way to do it. Based on the
> source IP address or source IP network of the packet, we can now
> jump to a specific gateway router.
>
> This is very useful for a specific use case of Kubernetes.
> When traffic is initiated inside a container heading to outside world,
> we want to be able to send such traffic outside the gateway router
> residing in the same host as that of the container. Since each
> host gets a specific subnet, we can use source IP address based
> policy routing to decide on the gateway router.
>
> Signed-off-by: Gurucharan Shetty <g...@ovn.org>
Maybe it is my own naivete, because I have not used policy-based routing
before, but it is not obvious to me how dst and src routes should
interact. Is it normal for a single routing table to contain both dst
and src routes? It appears from the implementation that if both are
present then they are applied using a longest-prefix-match approach
regardless of the field that matches. In the OpenFlow implementation, I
see that the meaning of the routing table is ambiguous when there are
src and dst routes with the same prefix length.
The two forks here are so similar:
char *match;
if (policy && !strcmp(policy, "src-ip")) {
match = xasprintf("ip4.src == "IP_FMT"/"IP_FMT,
IP_ARGS(network), IP_ARGS(mask));
} else {
match = xasprintf("ip4.dst == "IP_FMT"/"IP_FMT,
IP_ARGS(network), IP_ARGS(mask));
}
that I'd be inclined to factor it out, e.g.:
const char *dir = policy && !strcmp(policy, "src-ip") ? "src" : "dst";
char *match = xasprintf("ip4.%s == "IP_FMT"/"IP_FMT,
dir, IP_ARGS(network), IP_ARGS(mask));
I would have expected the new argument to the ovn-nbctl command to be
optional.
The ovn-nbctl manpage needs an update.
Acked-by: Ben Pfaff <b...@ovn.org>
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