bgpd: add set as-path exclude acl-list command

A route-map applied on incoming BGP updates is not able
to replace an unwanted as segments by another one.
unwanted as segment are based on an AS path access-list.

The below configuration illustrates the case:

router bgp 65001

address-family ipv4 unicast
 neighbor 192.168.1.2 route-map rule_2 in
exit-address-family

bgp as-path access-list RULE permit ^65

route-map rule_2 permit 10
 set as-path replace as-path-access-list RULE 6000

```
BGP routing table entry for 10.10.10.10/32, version 13
Paths: (1 available, best #1, table default)
  Advertised to non peer-group peers:
  192.168.10.65
  65000 1 2 3 123
    192.168.10.65 from 192.168.10.65 (10.10.10.11)
      Origin IGP, metric 0, valid, external, best (First path received)
```

After:

```
do show ip bgp 10.10.10.10/32
BGP routing table entry for 10.10.10.10/32, version 15
    Paths: (1 available, best #1, table default)
      Advertised to non peer-group peers:
      192.168.10.65
      6000 1 2 3 123
        192.168.10.65 from 192.168.10.65 (10.10.10.11)
          Origin IGP, metric 0, valid, external, best (First path
          received)
```

Signed-off-by: Francois Dumontet <francois.dumontet@6wind.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/bgpd/bgp_aspath.h b/bgpd/bgp_aspath.h
index b1a61d5b99..ebfc7d087d 100644
--- a/bgpd/bgp_aspath.h
+++ b/bgpd/bgp_aspath.h
@@ -107,6 +107,9 @@ extern unsigned int aspath_get_last_as(struct aspath *aspath);
 extern int aspath_loop_check(struct aspath *aspath, as_t asno);
 extern int aspath_loop_check_confed(struct aspath *aspath, as_t asno);
 extern bool aspath_private_as_check(struct aspath *aspath);
+extern struct aspath *aspath_replace_regex_asn(struct aspath *aspath,
+					       struct as_list *acl_list,
+					       as_t our_asn);
 extern struct aspath *aspath_replace_specific_asn(struct aspath *aspath,
 						  as_t target_asn,
 						  as_t our_asn);