route_src is a global defined as
const struct sockaddr route_src = { 2, PF_ROUTE, };

memcpy can be used here.

Index: rtsock.c
===================================================================
RCS file: /cvs/src/sys/net/rtsock.c,v
diff -u -p -r1.375 rtsock.c
--- rtsock.c	12 Jul 2024 17:20:18 -0000	1.375
+++ rtsock.c	2 Jan 2025 00:16:29 -0000
@@ -359,7 +359,7 @@ int
  route_peeraddr(struct socket *so, struct mbuf *nam)
  {
  	/* minimal support, just implement a fake peer address */
-	bcopy(&route_src, mtod(nam, caddr_t), route_src.sa_len);
+	memcpy(mtod(nam, caddr_t), &route_src, route_src.sa_len);
  	nam->m_len = route_src.sa_len;
  	return (0);
  }