Lets use a bit more const for the conffile.
The data conffile points to is most probably read-only.

-- 
:wq Claudio

Index: bgpd.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/bgpd.c,v
diff -u -p -r1.280 bgpd.c
--- bgpd.c	3 Dec 2024 13:46:53 -0000	1.280
+++ bgpd.c	12 Feb 2025 16:50:10 -0000
@@ -46,7 +46,7 @@ __dead void	usage(void);
 int		main(int, char *[]);
 pid_t		start_child(enum bgpd_process, char *, int, int, int);
 int		send_filterset(struct imsgbuf *, struct filter_set_head *);
-int		reconfigure(char *, struct bgpd_config *);
+int		reconfigure(const char *, struct bgpd_config *);
 int		send_config(struct bgpd_config *);
 int		dispatch_imsg(struct imsgbuf *, int, struct bgpd_config *);
 int		control_setup(struct bgpd_config *);
@@ -133,7 +133,7 @@ main(int argc, char *argv[])
 	struct connect_elm	*ce;
 	time_t			 timeout;
 	pid_t			 se_pid = 0, rde_pid = 0, rtr_pid = 0, pid;
-	char			*conffile;
+	const char		*conffile;
 	char			*saved_argv0;
 	u_int			 pfd_elms = 0, npfd, i;
 	int			 debug = 0;
@@ -572,7 +572,7 @@ send_filterset(struct imsgbuf *i, struct
 }
 
 int
-reconfigure(char *conffile, struct bgpd_config *conf)
+reconfigure(const char *conffile, struct bgpd_config *conf)
 {
 	struct bgpd_config	*new_conf;
 
Index: bgpd.h
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/bgpd.h,v
diff -u -p -r1.513 bgpd.h
--- bgpd.h	12 Feb 2025 16:40:51 -0000	1.513
+++ bgpd.h	12 Feb 2025 16:50:10 -0000
@@ -1544,7 +1544,7 @@ uint16_t	 pftable_ref(uint16_t);
 /* parse.y */
 int			cmdline_symset(char *);
 struct prefixset	*find_prefixset(char *, struct prefixset_head *);
-struct bgpd_config	*parse_config(char *, struct peer_head *,
+struct bgpd_config	*parse_config(const char *, struct peer_head *,
 			    struct rtr_config_head *);
 
 /* pftable.c */
Index: parse.y
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/parse.y,v
diff -u -p -r1.479 parse.y
--- parse.y	4 Feb 2025 18:16:56 -0000	1.479
+++ parse.y	12 Feb 2025 16:50:11 -0000
@@ -4099,7 +4099,8 @@ init_config(struct bgpd_config *c)
 }
 
 struct bgpd_config *
-parse_config(char *filename, struct peer_head *ph, struct rtr_config_head *rh)
+parse_config(const char *filename, struct peer_head *ph,
+    struct rtr_config_head *rh)
 {
 	struct sym		*sym, *next;
 	struct rde_rib		*rr;