zebra, lib, vtysh: Add CLI cmd to set/unset SRv6 encap source address

- Add a new node `SRV6_ENCAP_NODE` to the CLI graph. This node allows
users to configure encapsulation parameters for SRv6, including the
source address of the outer encapsulating IPv6 header.

- Install a new CLI command `source-address` under the
`SRV6_ENCAP_NODE` node. This command is used to configure the source
address of the outer encapsulating IPv6 header.

- Install a new CLI command `no source-address` under the
`SRV6_ENCAP_NODE` node. This command is used to unset the
source address of the outer encapsulating IPv6 header and restore the
default source address.

Examples:

```
router# segment-routing
router(sr)# srv6
router(srv6)# encapsulation
router(srv6-encap)# source-address fc00:0:1::1
```

```
router# segment-routing
router(sr)# srv6
router(srv6)# encapsulation
router(srv6-encap)# no source-address
```

Signed-off-by: Carmine Scarpitta <carmine.scarpitta@uniroma2.it>

1 files changed, 6 insertions, 0 deletions

diff --git a/zebra/zebra_srv6.h b/zebra/zebra_srv6.h
index 73876741fd..21936c3323 100644
--- a/zebra/zebra_srv6.h
+++ b/zebra/zebra_srv6.h
@@ -19,6 +19,9 @@
 /* SRv6 instance structure. */
 struct zebra_srv6 {
 	struct list *locators;
+
+	/* Source address for SRv6 encapsulation */
+	struct in6_addr encap_src_addr;
 };
 
 /* declare hooks for the basic API, so that it can be specialized or served
@@ -68,4 +71,7 @@ extern void srv6_manager_release_locator_chunk_call(struct zserv *client,
 extern int srv6_manager_client_disconnect_cb(struct zserv *client);
 extern int release_daemon_srv6_locator_chunks(struct zserv *client);
 
+extern void zebra_srv6_encap_src_addr_set(struct in6_addr *src_addr);
+extern void zebra_srv6_encap_src_addr_unset(void);
+
 #endif /* _ZEBRA_SRV6_H */