Commit bc84ba3a inserted a peer version placeholder. Embeddable
wireguard did not handle the flag WGPEER_A_PROTOCOL_VERSION and printed
the following warning:

    Warning: one or more unrecognized netlink attributes

This commit adds the field 'protocol_version' to the structure
'wg_peer'. It is equal to 0 if no protocol version were defined.
---
 contrib/examples/embeddable-wg-library/wireguard.c | 5 +++++
 contrib/examples/embeddable-wg-library/wireguard.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/contrib/examples/embeddable-wg-library/wireguard.c
b/contrib/examples/embeddable-wg-library/wireguard.c
index f0bdb5f..9610c50 100644
--- a/contrib/examples/embeddable-wg-library/wireguard.c
+++ b/contrib/examples/embeddable-wg-library/wireguard.c
@@ -66,6 +66,7 @@ enum wgpeer_attribute {
        WGPEER_A_RX_BYTES,
        WGPEER_A_TX_BYTES,
        WGPEER_A_ALLOWEDIPS,
+       WGPEER_A_PROTOCOL_VERSION,
        __WGPEER_A_LAST
 };

@@ -1326,6 +1327,10 @@ static int parse_peer(const struct nlattr
*attr, void *data)
                break;
        case WGPEER_A_ALLOWEDIPS:
                return mnl_attr_parse_nested(attr, parse_allowedips, peer);
+       case WGPEER_A_PROTOCOL_VERSION:
+               if (!mnl_attr_validate(attr, MNL_TYPE_U32))
+                       peer->protocol_version = mnl_attr_get_u32(attr);
+               break;
        default:
                warn_unrecognized("netlink");
        }
diff --git a/contrib/examples/embeddable-wg-library/wireguard.h
b/contrib/examples/embeddable-wg-library/wireguard.h
index e9210a4..2cee9ac 100644
--- a/contrib/examples/embeddable-wg-library/wireguard.h
+++ b/contrib/examples/embeddable-wg-library/wireguard.h
@@ -49,6 +49,7 @@ typedef struct wg_peer {
        struct timespec last_handshake_time;
        uint64_t rx_bytes, tx_bytes;
        uint16_t persistent_keepalive_interval;
+       uint32_t protocol_version;

        struct wg_allowedip *first_allowedip, *last_allowedip;
        struct wg_peer *next_peer;
--
2.19.2