bgpd: Add `set as-path replace <any|ASN>` cmd for route-maps

```
route-map tstas permit 10
 set as-path replace 1
exit
```

Before:

```
donatas-laptop(config-router-af)# do show ip bgp 10.10.10.10/32
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)
      Last update: Mon Apr 25 10:39:50 2022
```

After:

```
donatas-laptop(config-router-af)# 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
  65000 65010 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)
      Last update: Mon Apr 25 10:40:16 2022
```

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

8 files changed, 162 insertions, 0 deletions

diff --git a/tests/topotests/bgp_set_aspath_replace/__init__.py b/tests/topotests/bgp_set_aspath_replace/__init__.py
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/__init__.py
diff --git a/tests/topotests/bgp_set_aspath_replace/r1/bgpd.conf b/tests/topotests/bgp_set_aspath_replace/r1/bgpd.conf
new file mode 100644
index 000000000..1e98f4e49
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/r1/bgpd.conf
@@ -0,0 +1,17 @@
+!
+router bgp 65001
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.2 remote-as external
+ neighbor 192.168.1.2 timers 3 10
+ address-family ipv4 unicast
+  neighbor 192.168.1.2 route-map r2 in
+ exit-address-family
+!
+ip prefix-list p1 seq 5 permit 172.16.255.31/32
+!
+route-map r2 permit 10
+ match ip address prefix-list p1
+ set as-path replace 65003
+route-map r2 permit 20
+ set as-path replace any
+!
diff --git a/tests/topotests/bgp_set_aspath_replace/r1/zebra.conf b/tests/topotests/bgp_set_aspath_replace/r1/zebra.conf
new file mode 100644
index 000000000..acf120b20
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/r1/zebra.conf
@@ -0,0 +1,6 @@
+!
+interface r1-eth0
+ ip address 192.168.1.1/24
+!
+ip forwarding
+!
diff --git a/tests/topotests/bgp_set_aspath_replace/r2/bgpd.conf b/tests/topotests/bgp_set_aspath_replace/r2/bgpd.conf
new file mode 100644
index 000000000..23367f94f
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/r2/bgpd.conf
@@ -0,0 +1,8 @@
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.1.1 timers 3 10
+ neighbor 192.168.2.1 remote-as external
+ neighbor 192.168.2.1 timers 3 10
+!
diff --git a/tests/topotests/bgp_set_aspath_replace/r2/zebra.conf b/tests/topotests/bgp_set_aspath_replace/r2/zebra.conf
new file mode 100644
index 000000000..f22995434
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/r2/zebra.conf
@@ -0,0 +1,9 @@
+!
+interface r2-eth0
+ ip address 192.168.1.2/24
+!
+interface r2-eth1
+ ip address 192.168.2.2/24
+!
+ip forwarding
+!
diff --git a/tests/topotests/bgp_set_aspath_replace/r3/bgpd.conf b/tests/topotests/bgp_set_aspath_replace/r3/bgpd.conf
new file mode 100644
index 000000000..b7a7ceda1
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/r3/bgpd.conf
@@ -0,0 +1,9 @@
+!
+router bgp 65003
+ no bgp ebgp-requires-policy
+ neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers 3 10
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!
diff --git a/tests/topotests/bgp_set_aspath_replace/r3/zebra.conf b/tests/topotests/bgp_set_aspath_replace/r3/zebra.conf
new file mode 100644
index 000000000..3fa6c6448
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/r3/zebra.conf
@@ -0,0 +1,10 @@
+!
+int lo
+ ip address 172.16.255.31/32
+ ip address 172.16.255.32/32
+!
+interface r3-eth0
+ ip address 192.168.2.1/24
+!
+ip forwarding
+!
diff --git a/tests/topotests/bgp_set_aspath_replace/test_bgp_set_aspath_replace.py b/tests/topotests/bgp_set_aspath_replace/test_bgp_set_aspath_replace.py
new file mode 100644
index 000000000..d5549ae89
--- /dev/null
+++ b/tests/topotests/bgp_set_aspath_replace/test_bgp_set_aspath_replace.py
@@ -0,0 +1,103 @@
+#!/usr/bin/env python
+
+#
+# test_bgp_set_aspath_replace.py
+#
+# Copyright (c) 2022 by
+# Donatas Abraitis <donatas.abraitis@gmail.com>
+#
+# Permission to use, copy, modify, and/or distribute this software
+# for any purpose with or without fee is hereby granted, provided
+# that the above copyright notice and this permission notice appear
+# in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND NETDEF DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NETDEF BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+#
+
+"""
+Test if `set as-path replace` is working correctly for route-maps.
+"""
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+
+# pylint: disable=C0413
+from lib import topotest
+from lib.topogen import Topogen, TopoRouter, get_topogen
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for i, (rname, router) in enumerate(router_list.items(), 1):
+        router.load_config(
+            TopoRouter.RD_ZEBRA, os.path.join(CWD, "{}/zebra.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_BGP, os.path.join(CWD, "{}/bgpd.conf".format(rname))
+        )
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_bgp_maximum_prefix_out():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    def _bgp_converge(router):
+        output = json.loads(router.vtysh_cmd("show bgp ipv4 unicast json"))
+        expected = {
+            "routes": {
+                "172.16.255.31/32": [{"path": "65002 65001"}],
+                "172.16.255.32/32": [{"path": "65001 65001"}],
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_converge, tgen.gears["r1"])
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=0.5)
+
+    assert result is None, "Failed overriding incoming AS-PATH with route-map"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))