Fix implicit declaration of functions by including required system
headers and forward-declaring functions.

Modernize function arguments and specify function return types.

Fix verbose and debug functions to use a va_list.

Change send_pings to accept an int parameter because it is used as a
signal handler and that's how signal handlers are defined.
--- roverpingd/packet.c.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/packet.c	2021-11-23 05:52:10.000000000 -0600
@@ -3,6 +3,9 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 #include <sys/file.h>
 #include <sys/param.h>
 #include <sys/socket.h>
@@ -26,7 +29,7 @@
 
 /*------------------------------------------------------------------*/
 
-malloc_ping_packet()
+void malloc_ping_packet(void)
 {
   debug("mallocing %d bytes for packet\n", packet_size);
   if ((ping_packet = (u_char *)malloc((unsigned) packet_size)) == NULL) {
@@ -38,7 +41,7 @@
 
 /*------------------------------------------------------------------*/
 
-set_icmp_identifer()
+void set_icmp_identifer(void)
 {
   icmp_ident = getpid() & 0xffff;
   debug("setting icmp identifer to %d\n", icmp_ident);
@@ -46,9 +49,7 @@
 
 /*------------------------------------------------------------------*/
 
-static unsigned int calc_checksum(addr,len)
-u_short *addr;
-int len;
+static unsigned int calc_checksum(u_short *addr, int len)
 {
   register int nleft = len;
   register u_short *w = addr;
@@ -70,11 +71,7 @@
 
 /*------------------------------------------------------------------*/
 
-create_icmp_header(address,header,sock,seq)
-char *address;
-struct icmp *header;
-struct sockaddr *sock;
-int seq;
+int create_icmp_header(char *address, struct icmp *header, struct sockaddr *sock, int seq)
 {
   struct sockaddr_in *to;
 
--- roverpingd/pingd.c.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/pingd.c	2021-11-23 06:12:49.000000000 -0600
@@ -3,6 +3,9 @@
  */
 
 #include <stdio.h>
+#include <stdarg.h>
+#include <string.h>
+#include <unistd.h>
 #include <signal.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ -31,9 +34,7 @@
 
 /*------------------------------------------------------------------*/
 
-main(argc,argv)
-int argc;
-char *argv[];
+int main(int argc, char *argv[])
 {
   process_args(argc,argv);
   write_pid_file();
@@ -41,15 +42,13 @@
   malloc_ping_packet();
   set_icmp_identifer();
   read_ping_list();
-  send_pings();
+  send_pings(0);
   receive_pings(); 
 }
 
 /*------------------------------------------------------------------*/
 
-process_args(argc,argv)
-int argc;
-char *argv[];
+void process_args(int argc, char *argv[])
 {
   int flag;
   extern char *optarg;
@@ -98,7 +97,7 @@
 
 /*------------------------------------------------------------------*/
 
-usage()
+void usage(void)
 {
   printf("usage: nrg-pingd [args]\n");
   printf("  -p num   set polling interval to num (default %d secs)\n", polling_interval * NUM_DATA_POINTS);
@@ -111,37 +110,40 @@
 
 /*------------------------------------------------------------------*/
 
-debug(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o)
-char *a,*b,*c,*d,*e,*f,*g,*h,*i,*j,*k,*l,*m,*n,*o;
+void debug(const char* format, ...)
 {
+  va_list arglist;
   if ( debuggin ) {
-    fprintf(stderr,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o);
+    va_start(arglist, format);
+    vfprintf(stderr, format, arglist);
+    va_end(arglist);
     fflush(stderr);
   }
 }
 
 /*------------------------------------------------------------------*/
 
-verbose(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o)
-char *a,*b,*c,*d,*e,*f,*g,*h,*i,*j,*k,*l,*m,*n,*o;
+void verbose(const char* format, ...)
 {
   char time_str[27];
   time_t now_t = time(&now_t);
   int len;
+  va_list arglist;
   if ( verbosin && ! debuggin ) {
     strcpy(time_str,(char *)ctime(&now_t));
     len = strlen(time_str);
     time_str[len - 6] = '\0';
     fprintf(stderr,"%s ",time_str);
-    fprintf(stderr,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o);
+    va_start(arglist, format);
+    vfprintf(stderr, format, arglist);
+    va_end(arglist);
     fflush(stderr);
   }
 }
 
 /*------------------------------------------------------------------*/
 
-debug_ctime(t)
-time_t t;
+void debug_ctime(time_t t)
 {
   char time_str[27];
   int len;
@@ -156,8 +158,7 @@
 
 /*------------------------------------------------------------------*/
 
-dump_list_entry(i)
-int i;
+void dump_list_entry(int i)
 {
   fprintf(stderr,"list entry %d...\n",i);
   fprintf(stderr,"  n_addr is      \"%s\"\n",ping_list[i]->n_addr);
@@ -168,7 +169,7 @@
 
 /*------------------------------------------------------------------*/
 
-write_pid_file()
+void write_pid_file(void)
 {
   struct stat buf;
   FILE *fp;
--- roverpingd/pingd.h.in.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/pingd.h.in	2021-11-23 05:52:10.000000000 -0600
@@ -48,3 +48,16 @@
   int n_next_data_point;
 };
 
+void process_args(int argc, char *argv[]);
+void usage(void);
+void debug(const char* format, ...);
+void verbose(const char* format, ...);
+void debug_ctime(time_t t);
+void write_pid_file(void);
+void create_ping_socket(void);
+void malloc_ping_packet(void);
+void set_icmp_identifer(void);
+void read_ping_list(void);
+void send_pings(int sig);
+void receive_pings(void);
+int create_icmp_header(char *address, struct icmp *header, struct sockaddr *sock, int seq);
--- roverpingd/read_list.c.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/read_list.c	2021-11-23 05:52:10.000000000 -0600
@@ -3,6 +3,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <signal.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ -25,7 +26,7 @@
 
 /*------------------------------------------------------------------*/
 
-read_ping_list() 
+void read_ping_list(void)
 {
   struct stat buf;
   FILE *fp;
--- roverpingd/receive.c.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/receive.c	2021-11-23 05:52:10.000000000 -0600
@@ -3,6 +3,8 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/param.h>
 #include <sys/time.h>
 #include <sys/types.h>
@@ -33,11 +35,7 @@
 
 /*------------------------------------------------------------------*/
 
-int
-parse_icmp_seq(packet,packetlen,from)
-char *packet;
-int packetlen;
-struct sockaddr_in *from;
+int parse_icmp_seq(char *packet, int packetlen, struct sockaddr_in *from)
 {
   struct in_addr temp;
   struct ip *ip;
@@ -99,9 +97,7 @@
 
 /*------------------------------------------------------------------*/
 
-int
-calc_latency(idx)
-int idx;
+int calc_latency(int idx)
 {
   struct timeval now;
   int e_secs, e_usecs, rtt, ave_rtt;
@@ -118,7 +114,7 @@
 
 /*------------------------------------------------------------------*/
 
-receive_pings() 
+void receive_pings(void)
 {
   struct sockaddr_in from_sock;
   int from_len, byte_count, idx, l;
--- roverpingd/send.c.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/send.c	2021-11-23 05:52:10.000000000 -0600
@@ -3,6 +3,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <signal.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ -32,9 +33,12 @@
 static int nodes_pinged = 0;
 static time_t ping_list_start_time;
 
+void mark_node_as_down(int i);
+void set_alarm_itimer(time_t when_sec, time_t delta_ms);
+void write_stats_file(void);
 /*------------------------------------------------------------------*/
 
-void send_pings()
+void send_pings(int sig)
 {
   int i, rc;
   time_t now;
@@ -126,8 +130,7 @@
 
 /*------------------------------------------------------------------*/
 
-mark_node_as_down(i)
-int i;
+void mark_node_as_down(int i)
 {
   ping_list[i]->n_state = NOT_PINGING;
   ping_list[i]->n_latency = NOT_RESPONDING;
@@ -168,9 +171,7 @@
 
 /*------------------------------------------------------------------*/
 
-set_alarm_itimer(when_sec,delta_ms)
-time_t when_sec;
-time_t delta_ms;
+void set_alarm_itimer(time_t when_sec, time_t delta_ms)
 {
   time_t now;
   struct itimerval timer_time, old_timer_time;
@@ -197,7 +198,7 @@
 /*------------------------------------------------------------------*/
 
 #ifdef __DUMP_PACKETS__
-dump_packet()
+void dump_packet(void)
 {
   register int i;
   fprintf(stderr,"\n");
--- roverpingd/sock.c.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/sock.c	2021-11-23 05:52:10.000000000 -0600
@@ -3,6 +3,7 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/param.h>
 #include <sys/socket.h>
 #include <sys/time.h>
@@ -24,7 +25,7 @@
 
 /*------------------------------------------------------------------*/
 
-create_ping_socket()
+void create_ping_socket(void)
 {
   struct protoent *proto;
 
--- roverpingd/write_stats.c.orig	2006-01-30 06:12:24.000000000 -0600
+++ roverpingd/write_stats.c	2021-11-23 05:52:10.000000000 -0600
@@ -3,6 +3,8 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <signal.h>
 #ifdef __FreeBSD__
 #include <limits.h> 
@@ -27,9 +29,11 @@
 
 char pingstats_file[MAX_PATH_LENGTH];
 
+void dataprintf(FILE *fp, int arg);
+
 /*------------------------------------------------------------------*/
 
-write_stats_file()
+void write_stats_file(void)
 {
   FILE *fp;
   time_t now = time(&now);
@@ -111,9 +115,7 @@
 
 /*------------------------------------------------------------------*/
 
-dataprintf(fp, arg)
-FILE *fp;
-int arg;
+void dataprintf(FILE *fp, int arg)
 {
   switch (arg) {
     case NOT_RESPONDING: {