[fpmsyncd] Add support for SRv6

[cscarpitta]

The dplane_fpm_nl module in FRR allows SONiC to learn the forwarding information computed by FRR. FRR already supports many SRv6 functionalities. There is an open PR (FRRouting/frr/pull/12301) to extend the dplane_fpm_nl module of FRR to export the required SRv6 information to SONiC.

OrchAgent (specifically, RouteOrch and SRv6Orch) in SONiC SWSS can already extract the SRv6 information from the APP_DB and push it towards the ASIC_DB (sonic-net/sonic-swss/pull/1964).

However, the fpmsyncd in SONiC SWSS does not process the SRv6 information received from FRR. This PR extends fpmsyncd to parse the SRv6 information received from FRR and push it toward the APP_DB.

What I did

I added support for SRv6 to fpmsyncd:

• I added a handler onSrv6RouteMsg() which is able to parse Netlink messages containing an SRv6 Steering Route and create an entry in the ROUTE_TABLE of APP_DB.
• I added a handler onSrv6LocalSidMsg() which is able to parse Netlink messages containing an SRv6 Local SID and create an entry in the SRV6_MY_SID_TABLE of APP_DB.
• I changed onMsgRaw() to pass the Netlink messages to the appropriate handler depending on the encapsulation type.
• I added the unit tests to verify that fpmsyncd processes the Netlink messages and updates the APP_DB correctly.

Why I did it

FRR supports many SRv6 functionalities. There is an open PR (FRRouting/frr/pull/12301) to extend the dplane_fpm_nl module of FRR to export the required SRv6 information to SONiC.

However, the fpmsyncd in SONiC SWSS did not process the SRv6 information received from FRR.

How I verified it

I added new unit tests in tests/mock_tests/fpmsyncd/receive_srv6_localsids_ut.cpp and tests/mock_tests/fpmsyncd/receive_srv6_steer_routes_ut.cpp.

Details if related SRv6 HLD: https://github.com/sonic-net/SONiC/blob/master/doc/srv6/srv6_hld.md SRv6 uSID HLD: https://github.com/sonic-net/SONiC/blob/master/doc/srv6/SRv6_uSID.md

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: cscarpitta / name: Carmine Scarpitta (5ad6686952b699f677fb41a9d694b5ff9174d9ca, 5081801b868bfb2f23385d7bc39a21000cc2a8ad, f50814ed1b69758bf0a392d65b1558499a95ac91, f9a7cdff312d855c16c1e646c5cde3f2330b9fa8, 3dfa88dd65902d3b250db36c5c60c245c1047b33, cab3b30f17ad80883b98a366441f1c38899cb1cc)

[reshmaintel]

@svshah-intel Hi Shitanshu, could you please help review this PR. Thanks.

[cscarpitta]

@svshah-intel Many thanks for your review! I addressed all your comments. Could you please take another look?