BGP Add-Path RX Cannot Be Disabled.

[dteach-rv]

Hello,

The FRR bgp daemon should have the ability to disable add-path negotiation completely. Currently, the add-path RX capability is hardcoded into the daemon. This seems like a bad idea as the only way one would be able to stop receiving add-path enabled routes from a peer who has negotiated add-path TX would be to disable that peer completely.

Steps To Reproduce.

Establish peering with a BGP add-path TX or both.
Advertise multiple paths via bgp add-path with the path ID in the bgp update NLRI.

Expected Behavior:
Frr should have a global or per-afi-safi command to allow add-path RX to be disabled.

-OS Version: CentOS Linux release 7.9.2009 (Core)
-Kernel Version: Linux frr.routeviews.org 3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
-FRR Version:

Copyright 1996-2005 Kunihiro Ishiguro, et al.
configured with:
'--build=x86_64-redhat-linux-gnu' '--host=x86_64-redhat-linux-gnu' '--program-prefix=' '--disable-dependency-tracking' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sysconfdir=/etc' '--datadir=/usr/share' '--includedir=/usr/include' '--libdir=/usr/lib64' '--libexecdir=/usr/libexec' '--localstatedir=/var' '--sharedstatedir=/var/lib' '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--sbindir=/usr/lib/frr' '--sysconfdir=/etc/frr' '--localstatedir=/var/run/frr' '--disable-static' '--disable-werror' '--enable-irdp' '--enable-multipath=256' '--enable-vtysh' '--enable-ospfclient' '--enable-ospfapi' '--disable-rtadv' '--disable-ldpd' '--disable-pimd' '--disable-pbrd' '--disable-nhrpd' '--enable-eigrpd' '--disable-babeld' '--disable-vrrpd' '--enable-user=frr' '--enable-group=frr' '--enable-vty-group=frrvty' '--disable-fpm' '--enable-watchfrr' '--disable-bgp-vnc' '--enable-isisd' '--enable-systemd' '--enable-rpki' '--disable-bfdd' '--enable-privileged-vty' '--enable-snmp' 'build_alias=x86_64-redhat-linux-gnu' 'host_alias=x86_64-redhat-linux-gnu' 'PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'```

[dteach-rv]

#RIPE-NCC/bgpdump#9

[ton31337]

Implemented in #9545.