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, 17 insertions, 0 deletions

diff --git a/zebra/zebra_srv6.c b/zebra/zebra_srv6.c
index ee463c76a8..adc7d32aae 100644
--- a/zebra/zebra_srv6.c
+++ b/zebra/zebra_srv6.c
@@ -409,6 +409,23 @@ int release_daemon_srv6_locator_chunks(struct zserv *client)
 	return count;
 }
 
+void zebra_srv6_encap_src_addr_set(struct in6_addr *encap_src_addr)
+{
+	struct zebra_srv6 *srv6 = zebra_srv6_get_default();
+
+	if (!encap_src_addr)
+		return;
+
+	memcpy(&srv6->encap_src_addr, encap_src_addr, sizeof(struct in6_addr));
+}
+
+void zebra_srv6_encap_src_addr_unset(void)
+{
+	struct zebra_srv6 *srv6 = zebra_srv6_get_default();
+
+	memset(&srv6->encap_src_addr, 0, sizeof(struct in6_addr));
+}
+
 void zebra_srv6_terminate(void)
 {
 	struct srv6_locator *locator;