bgpd: add 'neighbor x.x.x.x allowas-in origin' knob

bgpd: add 'neighbor x.x.x.x allowas-in origin' knob

Signed-off-by: Daniel Walton <dwalton@cumulusnetworks.com>
Reviewed-by:   Don Slice <dslice@cumulusnetworks.com>
Ticket: CM-13207

normal table on spine-1....we do not see 6.0.0.10 (spine-2's loopback)
spine-1 and spine-2 are in AS 65200

superm-redxp-05# show ip bgp
BGP table version is 13, local router ID is 6.0.0.9
Status codes: s suppressed, d damped, h history, * valid, > best, =
multipath,
              i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 6.0.0.5/32       swp1            0              0 65101 ?
*> 6.0.0.6/32       swp2            0              0 65101 ?
*> 6.0.0.7/32       swp3            0              0 65104 ?
*> 6.0.0.8/32       swp4            0              0 65104 ?
*> 6.0.0.9/32       0.0.0.0                  0          32768 ?
*= 6.0.0.11/32      swp2                          0 65101 65001 ?
*>                  swp1                          0 65101 65001 ?
*= 6.0.0.12/32      swp2                          0 65101 65002 ?
*>                  swp1                          0 65101 65002 ?
*= 6.0.0.13/32      swp4                          0 65104 65001 ?
*>                  swp3                          0 65104 65001 ?
*= 6.0.0.14/32      swp4                          0 65104 65002 ?
*>                  swp3                          0 65104 65002 ?

Displayed  9 out of 13 total prefixes
superm-redxp-05#

spine-1 with "neighbor x.x.x.x allowas-in origin", we now see 6.0.0.10

superm-redxp-05# show ip bgp
BGP table version is 14, local router ID is 6.0.0.9
Status codes: s suppressed, d damped, h history, * valid, > best, =
multipath,
              i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 6.0.0.5/32       swp1            0              0 65101 ?
*> 6.0.0.6/32       swp2            0              0 65101 ?
*> 6.0.0.7/32       swp3            0              0 65104 ?
*> 6.0.0.8/32       swp4            0              0 65104 ?
*  6.0.0.9/32       swp2                          0 65101 65200 ?
*                   swp1                          0 65101 65200 ?
*                   swp3                          0 65104 65200 ?
*                   swp4                          0 65104 65200 ?
*>                  0.0.0.0                  0          32768 ?
*= 6.0.0.10/32      swp2                          0 65101 65200 ?
*>                  swp1                          0 65101 65200 ?
*=                  swp3                          0 65104 65200 ?
*=                  swp4                          0 65104 65200 ?
*= 6.0.0.11/32      swp2                          0 65101 65001 ?
*>                  swp1                          0 65101 65001 ?
*= 6.0.0.12/32      swp2                          0 65101 65002 ?
*>                  swp1                          0 65101 65002 ?
*= 6.0.0.13/32      swp4                          0 65104 65001 ?
*>                  swp3                          0 65104 65001 ?
*= 6.0.0.14/32      swp4                          0 65104 65002 ?
*>                  swp3                          0 65104 65002 ?

Displayed  10 out of 21 total prefixes
superm-redxp-05#

The only as-paths with 65200 that made it through were the ones that
originated from 65200

superm-redxp-05# show ip bgp regexp _65200_
BGP table version is 14, local router ID is 6.0.0.9
Status codes: s suppressed, d damped, h history, * valid, > best, =
multipath,
              i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*  6.0.0.9/32       swp2                          0 65101 65200 ?
*                   swp1                          0 65101 65200 ?
*                   swp3                          0 65104 65200 ?
*                   swp4                          0 65104 65200 ?
*= 6.0.0.10/32      swp2                          0 65101 65200 ?
*>                  swp1                          0 65101 65200 ?
*=                  swp3                          0 65104 65200 ?
*=                  swp4                          0 65104 65200 ?

Displayed  2 out of 21 total prefixes
superm-redxp-05#