Merge pull request #2416 from pi-hole/tweak/search_proc

Check for existing NTP client when starting FTL

src/ntp/client.c

@@ -41,6 +41,8 @@
 #include "database/message-table.h"
 // check_capability()
 #include "capabilities.h"
+// search_proc()
+#include "procps.h"
 
 // Required accuracy of the NTP sync in seconds in order to start the NTP server
 // thread. If the NTP sync is less accurate than this value, the NTP server
@@ -746,6 +748,13 @@ bool ntp_start_sync_thread(pthread_attr_t *attr)
 		ntp_server_start();
 		return false;
 	}
+	// Return early if a clock disciplining NTP client is detected
+	// Checks chrony, the ntp family (ntp, ntpsec and openntpd), and ntpd-rs
+	if(search_proc("chronyd") > 0 || search_proc("ntpd") > 0 || search_proc("ntp-daemon") > 0)
+	{
+		log_info("Clock disciplining NTP client detected, not starting embedded NTP client/server");
+		return false;
+	}
 
 	// Check if we have the ambient capabilities to set the system time.
 	// Without CAP_SYS_TIME, we cannot set the system time and the NTP

src/procps.c

@@ -359,3 +359,59 @@ bool parse_proc_stat(unsigned long *total_sum, unsigned long *idle_sum)
 
 	return true;
 }
+
+/**
+ * @brief Searches for a process by its name in the /proc filesystem.
+ *
+ * This function iterates through the directories in /proc, which represent
+ * process IDs (PIDs), and checks the "comm" file in each directory to find
+ * a process with a matching name.
+ *
+ * @param name The name of the process to search for.
+ *
+ * @return The PID of the process if found, or -1 if no matching process is found
+ *         or if an error occurs (e.g., unable to open /proc or a file).
+ *
+ * @note This function assumes the /proc filesystem is available and accessible.
+ *       It also assumes that the "comm" file in each process directory contains
+ *       the name of the process.
+ */
+pid_t search_proc(const char *name)
+{
+	DIR *dir = opendir("/proc");
+	if(dir == NULL)
+		return -1;
+
+	struct dirent *entry;
+	while((entry = readdir(dir)) != NULL)
+	{
+		// Check if the entry is a directory and contains only digits
+		// We skip ".", "..", "self", and friends
+		if(entry->d_type == DT_DIR && isdigit(entry->d_name[0]))
+		{
+			char filename[64];
+			snprintf(filename, sizeof(filename), "/proc/%s/comm", entry->d_name);
+			FILE *file = fopen(filename, "r");
+			if(file != NULL)
+			{
+				char comm[PROC_PATH_SIZ + 1] = { 0 };
+				// Read the command name from the file
+				if(fscanf(file, "%"xstr(PROC_PATH_SIZ)"s", comm) == 1)
+				{
+					if(strcmp(comm, name) == 0)
+					{
+						// Found a matching process
+						fclose(file);
+						closedir(dir);
+						return atoi(entry->d_name);
+					}
+				}
+				fclose(file);
+			}
+		}
+	}
+
+	// No process found with the given name
+	closedir(dir);
+	return -1;
+}

src/procps.h

@@ -49,5 +49,6 @@ struct proc_meminfo {
 bool getProcessMemory(struct proc_mem *mem, const unsigned long total_memory);
 bool parse_proc_meminfo(struct proc_meminfo *mem);
 bool parse_proc_stat(unsigned long *total_sum, unsigned long *idle_sum);
+pid_t search_proc(const char *name);
 
 #endif // PROCPS_H