diff --git a/ndhc/arp.h b/ndhc/arp.h
index 49c5a03..ef8f8db 100644
--- a/ndhc/arp.h
+++ b/ndhc/arp.h
@@ -59,14 +59,14 @@ extern int arp_probe_min;
 extern int arp_probe_max;
 extern int arp_relentless_def;
 
-extern void arp_reset_send_stats(void);
-extern int arp_close_fd(struct client_state_t *cs);
-extern int arp_check(struct client_state_t *cs, struct dhcpmsg *packet);
-extern int arp_gw_check(struct client_state_t *cs);
-extern void arp_set_defense_mode(struct client_state_t *cs);
-extern void arp_success(struct client_state_t *cs);
-extern void handle_arp_response(struct client_state_t *cs);
-extern void handle_arp_timeout(struct client_state_t *cs, long long nowts);
-extern long long arp_get_wake_ts(void);
+void arp_reset_send_stats(void);
+int arp_close_fd(struct client_state_t *cs);
+int arp_check(struct client_state_t *cs, struct dhcpmsg *packet);
+int arp_gw_check(struct client_state_t *cs);
+void arp_set_defense_mode(struct client_state_t *cs);
+void arp_success(struct client_state_t *cs);
+void handle_arp_response(struct client_state_t *cs);
+void handle_arp_timeout(struct client_state_t *cs, long long nowts);
+long long arp_get_wake_ts(void);
 
 #endif /* ARP_H_ */
diff --git a/ndhc/dhcp.h b/ndhc/dhcp.h
index a1d8cc1..f2ce3c1 100644
--- a/ndhc/dhcp.h
+++ b/ndhc/dhcp.h
@@ -80,15 +80,15 @@ struct udp_dhcp_packet {
     struct dhcpmsg data;
 };
 
-extern void set_listen_raw(struct client_state_t *cs);
-extern void set_listen_cooked(struct client_state_t *cs);
-extern void set_listen_none(struct client_state_t *cs);
-extern void handle_packet(struct client_state_t *cs);
-extern int send_discover(struct client_state_t *cs);
-extern int send_selecting(struct client_state_t *cs);
-extern int send_renew(struct client_state_t *cs);
-extern int send_rebind(struct client_state_t *cs);
-extern int send_decline(struct client_state_t *cs, uint32_t server);
-extern int send_release(struct client_state_t *cs);
+void set_listen_raw(struct client_state_t *cs);
+void set_listen_cooked(struct client_state_t *cs);
+void set_listen_none(struct client_state_t *cs);
+void handle_packet(struct client_state_t *cs);
+int send_discover(struct client_state_t *cs);
+int send_selecting(struct client_state_t *cs);
+int send_renew(struct client_state_t *cs);
+int send_rebind(struct client_state_t *cs);
+int send_decline(struct client_state_t *cs, uint32_t server);
+int send_release(struct client_state_t *cs);
 
 #endif
diff --git a/ndhc/ifchd-parse.h b/ndhc/ifchd-parse.h
index 092ccb8..276d091 100644
--- a/ndhc/ifchd-parse.h
+++ b/ndhc/ifchd-parse.h
@@ -29,6 +29,6 @@
 #ifndef _NJK_NDHC_IFCHD_PARSE_H_
 #define _NJK_NDHC_IFCHD_PARSE_H_
 
-extern int execute_buffer(char *newbuf);
+int execute_buffer(char *newbuf);
 
 #endif /* _NJK_NDHC_IFCHD_PARSE_H_ */
diff --git a/ndhc/ifchd.h b/ndhc/ifchd.h
index 886cd46..ac8a004 100644
--- a/ndhc/ifchd.h
+++ b/ndhc/ifchd.h
@@ -36,17 +36,17 @@ extern char pidfile_ifch[MAX_PATH_LENGTH];
 extern uid_t ifch_uid;
 extern gid_t ifch_gid;
 
-extern void perform_timezone(const char *str, size_t len);
-extern void perform_dns(const char *str, size_t len);
-extern void perform_lprsvr(const char *str, size_t len);
-extern void perform_hostname(const char *str, size_t len);
-extern void perform_domain(const char *str, size_t len);
-extern void perform_ipttl(const char *str, size_t len);
-extern void perform_ntpsrv(const char *str, size_t len);
-extern void perform_wins(const char *str, size_t len);
+void perform_timezone(const char *str, size_t len);
+void perform_dns(const char *str, size_t len);
+void perform_lprsvr(const char *str, size_t len);
+void perform_hostname(const char *str, size_t len);
+void perform_domain(const char *str, size_t len);
+void perform_ipttl(const char *str, size_t len);
+void perform_ntpsrv(const char *str, size_t len);
+void perform_wins(const char *str, size_t len);
 
-extern void do_ifch_work(void);
-extern void ifch_main(void);
+void do_ifch_work(void);
+void ifch_main(void);
 
 #endif /* NJK_IFCHD_H_ */
 
diff --git a/ndhc/ifset.h b/ndhc/ifset.h
index 19cdbf2..783c418 100644
--- a/ndhc/ifset.h
+++ b/ndhc/ifset.h
@@ -28,11 +28,11 @@
 
 #ifndef NJK_IFSET_H_
 #define NJK_IFSET_H_
-extern int perform_ifup(void);
-extern void perform_ip_subnet_bcast(const char *str_ipaddr,
-                                    const char *str_subnet,
-                                    const char *str_bcast);
-extern void perform_router(const char *str, size_t len);
-extern void perform_mtu(const char *str, size_t len);
+int perform_ifup(void);
+void perform_ip_subnet_bcast(const char *str_ipaddr,
+                             const char *str_subnet,
+                             const char *str_bcast);
+void perform_router(const char *str, size_t len);
+void perform_mtu(const char *str, size_t len);
 #endif
 
diff --git a/ndhc/leasefile.h b/ndhc/leasefile.h
index bb2b9b7..1ab81fa 100644
--- a/ndhc/leasefile.h
+++ b/ndhc/leasefile.h
@@ -29,9 +29,9 @@
 #ifndef NJK_NDHC_LEASEFILE_H_
 #define NJK_NDHC_LEASEFILE_H_
 
-extern void set_leasefile(char *lf);
-extern void open_leasefile(void);
-extern void write_leasefile(struct in_addr ipnum);
+void set_leasefile(char *lf);
+void open_leasefile(void);
+void write_leasefile(struct in_addr ipnum);
 
 #endif /* NJK_NDHC_LEASEFILE_H_ */
 
diff --git a/ndhc/ndhc.h b/ndhc/ndhc.h
index f34a461..46bad76 100644
--- a/ndhc/ndhc.h
+++ b/ndhc/ndhc.h
@@ -73,6 +73,6 @@ extern int pToNdhcW;
 extern char chroot_dir[MAX_PATH_LENGTH];
 extern char resolv_conf_d[MAX_PATH_LENGTH];
 
-extern void background(void);
+void background(void);
 
 #endif /* NJK_NDHC_NDHC_H_ */
diff --git a/ndhc/netlink.h b/ndhc/netlink.h
index e2e3d7a..3c2effc 100644
--- a/ndhc/netlink.h
+++ b/ndhc/netlink.h
@@ -40,7 +40,7 @@ enum {
     IFS_REMOVED
 };
 
-extern void handle_nl_message(struct client_state_t *cs);
-extern int nl_getifdata(void);
+void handle_nl_message(struct client_state_t *cs);
+int nl_getifdata(void);
 
 #endif /* NK_NETLINK_H_ */
diff --git a/ndhc/nl.h b/ndhc/nl.h
index cf03ea7..21f47a2 100644
--- a/ndhc/nl.h
+++ b/ndhc/nl.h
@@ -41,23 +41,23 @@ static inline int nlmsg_get_error(const struct nlmsghdr *nlh)
     return err->error & 0x7fffffff;
 }
 
-extern int rtattr_assign(struct rtattr *attr, int type, void *data);
-extern int nl_add_rtattr(struct nlmsghdr *n, size_t max_length, int type,
-                         const void *data, size_t data_length);
+int rtattr_assign(struct rtattr *attr, int type, void *data);
+int nl_add_rtattr(struct nlmsghdr *n, size_t max_length, int type,
+                  const void *data, size_t data_length);
 typedef int (*nl_rtattr_parse_fn)(struct rtattr *attr, int type, void *data);
-extern void nl_rtattr_parse(const struct nlmsghdr *nlh, size_t offset,
-                            nl_rtattr_parse_fn workfn, void *data);
+void nl_rtattr_parse(const struct nlmsghdr *nlh, size_t offset,
+                     nl_rtattr_parse_fn workfn, void *data);
 
-extern ssize_t nl_recv_buf(int fd, char *buf, size_t blen);
+ssize_t nl_recv_buf(int fd, char *buf, size_t blen);
 
 typedef void (*nlmsg_foreach_fn)(const struct nlmsghdr *, void *);
-extern int nl_foreach_nlmsg(char *buf, size_t blen, uint32_t seq,
-                            uint32_t portid,
-                            nlmsg_foreach_fn pfn, void *fnarg);
-extern int nl_sendgetlinks(int fd, int seq);
-extern int nl_sendgetlink(int fd, int seq, int ifindex);
-extern int nl_sendgetaddr(int fd, int seq, int ifindex);
+int nl_foreach_nlmsg(char *buf, size_t blen, uint32_t seq,
+                     uint32_t portid,
+                     nlmsg_foreach_fn pfn, void *fnarg);
+int nl_sendgetlinks(int fd, int seq);
+int nl_sendgetlink(int fd, int seq, int ifindex);
+int nl_sendgetaddr(int fd, int seq, int ifindex);
 
-extern int nl_open(int nltype, int nlgroup, int *nlportid);
+int nl_open(int nltype, int nlgroup, int *nlportid);
 
 #endif /* NK_NL_H_ */
diff --git a/ndhc/seccomp.h b/ndhc/seccomp.h
index e63b5c1..860d492 100644
--- a/ndhc/seccomp.h
+++ b/ndhc/seccomp.h
@@ -32,7 +32,7 @@
 
 extern bool seccomp_enforce;
 
-extern int enforce_seccomp_ndhc(void);
-extern int enforce_seccomp_ifch(void);
+int enforce_seccomp_ndhc(void);
+int enforce_seccomp_ifch(void);
 
 #endif /* NJK_NDHC_SECCOMP_H_ */
diff --git a/ndhc/state.h b/ndhc/state.h
index 62e007e..1d5cbf9 100644
--- a/ndhc/state.h
+++ b/ndhc/state.h
@@ -43,18 +43,18 @@ typedef enum {
     DS_NUM_STATES,
 } dhcp_states_t;
 
-extern void reinit_selecting(struct client_state_t *cs, int timeout);
+void reinit_selecting(struct client_state_t *cs, int timeout);
 
-extern void packet_action(struct client_state_t *cs, struct dhcpmsg *packet,
+void packet_action(struct client_state_t *cs, struct dhcpmsg *packet,
                    uint8_t msgtype);
-extern void timeout_action(struct client_state_t *cs, long long nowts);
-extern void force_renew_action(struct client_state_t *cs);
-extern void force_release_action(struct client_state_t *cs);
+void timeout_action(struct client_state_t *cs, long long nowts);
+void force_renew_action(struct client_state_t *cs);
+void force_release_action(struct client_state_t *cs);
 
-extern void ifup_action(struct client_state_t *cs);
-extern void ifnocarrier_action(struct client_state_t *cs);
-extern void ifdown_action(struct client_state_t *cs);
-extern long long dhcp_get_wake_ts(void);
+void ifup_action(struct client_state_t *cs);
+void ifnocarrier_action(struct client_state_t *cs);
+void ifdown_action(struct client_state_t *cs);
+long long dhcp_get_wake_ts(void);
 
 #endif
 
diff --git a/ndhc/sys.h b/ndhc/sys.h
index 63e8143..f4e528c 100644
--- a/ndhc/sys.h
+++ b/ndhc/sys.h
@@ -38,7 +38,7 @@ static inline unsigned long long curms()
     return ts.tv_sec * 1000ULL + ts.tv_nsec / 1000000ULL;
 }
 
-extern void epoll_add(int epfd, int fd);
-extern void epoll_del(int epfd, int fd);
+void epoll_add(int epfd, int fd);
+void epoll_del(int epfd, int fd);
 
 #endif /* SYS_H_ */