What should happen if there is no routing-policy configured?

[dplore]

Routing-policy describes what should happen when a policy is defined and applied.

public/release/models/policy/openconfig-routing-policy.yang

Lines 45 to 49 in 0bd6815

	Policy definitions are referenced in routing protocol
	configurations using import and export configuration statements.
	The arguments are members of an ordered list of named policy
	definitions which comprise a policy chain, and optionally, an
	explicit default policy action (i.e., reject or accept).

But there is not an explicit definition of what should happen if no policy is applied. For example, if a BGP session is configured, but no policy is configured for that session, I interpret that there is no policy and therefore all routes are accepted. If a policy is applied to a session, then the rules for that policy are enforced. (including for example, the default-import-policy which is REJECT)

Do we need a clarification to the description of the routing-policy module?

[LimeHat]

For EBGP the behavior is standardized in RFC 8212

[sachendras]

I think, no-policy (including no default policy defined) for import and export == allow-all should only be applicable to IBGP.
For EBGP, no-policy (including no default policy defined) == deny-all for both import and export policies. This will keep EBGP behavior compliant with RFC8212

[rszarecki]

default-(import|export)-policy is bad name it should by rathter default-(import|export)-action. IMO it applys as follow:

• if no policy is configuterd, then default-(import|export)-policy is applied to all recived/advertised routes.
• if policy/policiey-chain is configuterd,, but recived/advertised route do not match any statement, then default-(import|export)-policy is applied
• if policy/policiey-chain is configuterd, recived/advertised route do match some statement, bu non of matched statement has route disposal (accept reject) action configured, then default-(import|export)-policy is applied.
• if default-(import|export)-policy is NOT configured, and on of above conditions is met, then iBGP accept all revived/advertised routes, and eBGP reject all revived/advertised routes (RFC8212)

[sachendras]

default-(import|export)-policy is bad name it should by rathter default-(import|export)-action. IMO it applys as follow:

• if no policy is configuterd, then default-(import|export)-policy is applied to all recived/advertised routes.
• if policy/policiey-chain is configuterd,, but recived/advertised route do not match any statement, then default-(import|export)-policy is applied
• if policy/policiey-chain is configuterd, recived/advertised route do match some statement, bu non of matched statement has route disposal (accept reject) action configured, then default-(import|export)-policy is applied.
• if default-(import|export)-policy is NOT configured, and on of above conditions is met, then iBGP accept all revived/advertised routes, and eBGP reject all revived/advertised routes (RFC8212)

Probably openconfig/featureprofiles#2272 should help?

[robshakir]

In YANG, if a container is a non-presence container then it is assumed to exist -- thus, if we have .../afi-safis/afi-safi[afi-safi-name=IPV4_UNICAST] created (which we must to enabled the AFI-SAFI) then by default the apply-policy/default-(import|export)-policy leaves are populated with the default value -- and hence an unspecified policy and unspecified default action means REJECT_ROUTE.

Of course, relying on the YANG semantics here is complicated, so I suggest a clarification in the description would be useful.

[dplore]

Based on the current yang, an an unspecified policy and unspecified default action means eBGP AND iBGP both have REJECT_ROUTE applied. TO accept routes, one must explicitly add a policy OR explicitly change the default action to ACCEPT_ROUTE.

I will submit a PR to clarify the policy description. A subsequent PR could further change the model if the community wants to change this behavior.