get_line now uses a single buffer, strips leading space and skips comments. This reduces malloc usage slightly and gives a cleaner API at the expense of a slight bss increase.

common.c

@@ -51,31 +51,64 @@
 #  define _PATH_DEVNULL "/dev/null"
 #endif
 
-int clock_monotonic = 0;
+int clock_monotonic;
+static char *lbuf;
+static size_t lbuf_len;
+
+#ifdef DEBUG_MEMORY
+static void
+free_lbuf(void)
+{
+	free(lbuf);
+}
+#endif
 
 /* Handy routine to read very long lines in text files.
- * This means we read the whole line and avoid any nasty buffer overflows. */
-ssize_t
-get_line(char **line, size_t *len, FILE *fp)
+ * This means we read the whole line and avoid any nasty buffer overflows.
+ * We strip leading space and avoid comment lines, making the code that calls
+ * us smaller.
+ * As we don't use threads, this API is clean too. */
+char *
+get_line(FILE * restrict fp)
 {
-	char *p;
-	size_t last = 0;
+	char *p, *e;
+	size_t last;
 
-	while(!feof(fp)) {
-		if (*line == NULL || last != 0) {
-			*len += BUFSIZ;
-			*line = xrealloc(*line, *len);
+again:
+	if (feof(fp))
+		return NULL;
+
+#ifdef DEBUG_MEMORY
+	if (!lbuf)
+		atexit(free_lbuf);
+#endif
+
+	last = 0;
+	do {
+		if (!lbuf || last != 0) {
+			lbuf_len += BUFSIZ;
+			lbuf = xrealloc(lbuf, lbuf_len);
 		}
-		p = *line + last;
+		p = lbuf + last;
 		memset(p, 0, BUFSIZ);
 		fgets(p, BUFSIZ, fp);
 		last += strlen(p);
-		if (last && (*line)[last - 1] == '\n') {
-			(*line)[last - 1] = '\0';
+		if (last && lbuf[last - 1] == '\n') {
+			lbuf[last - 1] = '\0';
 			break;
 		}
+	} while(!feof(fp));
+	if (!last)
+		return NULL;
+
+	e = p + last - 1;
+	for (p = lbuf; p < e; p++) {
+		if (*p != ' ' && *p != '\t')
+			break;
 	}
-	return last;
+	if (p == e || *p == '#' || *p == ';')
+		goto again;
+	return p;
 }
 
 /* Simple hack to return a random number without arc4random */

common.h

@@ -86,7 +86,7 @@ int closefrom(int);
 
 int set_cloexec(int);
 int set_nonblock(int);
-ssize_t get_line(char **, size_t *, FILE *);
+char *get_line(FILE * restrict);
 extern int clock_monotonic;
 int get_monotonic(struct timeval *);
 time_t uptime(void);

duid.c

@@ -47,30 +47,23 @@ get_duid(unsigned char *duid, const struct interface *iface)
 	time_t t;
 	int x = 0;
 	unsigned char *p = duid;
-	size_t len = 0, l = 0;
-	char *buffer = NULL, *line, *option;
+	size_t len = 0;
+	char *line;
 
 	/* If we already have a DUID then use it as it's never supposed
 	 * to change once we have one even if the interfaces do */
 	if ((f = fopen(DUID, "r"))) {
-		while ((get_line(&buffer, &len, f))) {
-			line = buffer;
-			while ((option = strsep(&line, " \t")))
-				if (*option != '\0')
-					break;
-			if (!option || *option == '\0' || *option == '#')
-				continue;
-			l = hwaddr_aton(NULL, option);
-			if (l && l <= DUID_LEN) {
-				hwaddr_aton(duid, option);
+		while ((line = get_line(f))) {
+			len = hwaddr_aton(NULL, line);
+			if (len && len <= DUID_LEN) {
+				hwaddr_aton(duid, line);
 				break;
 			}
-			l = 0;
+			len = 0;
 		}
 		fclose(f);
-		free(buffer);
-		if (l)
-			return l;
+		if (len)
+			return len;
 	} else {
 		if (errno != ENOENT)
 			return 0;

if-linux.c

@@ -431,18 +431,15 @@ struct interface *
 discover_interfaces(int argc, char * const *argv)
 {
 	FILE *f;
-	char *buffer = NULL, *p;
-	size_t len = 0, ln = 0, n;
+	char *p;
+	size_t ln = 0, n;
 	int i;
 	struct interface *ifs = NULL, *ifp, *ifl;
 
 	if ((f = fopen("/proc/net/dev", "r"))) {
-		while (get_line(&buffer, &len, f)) {
+		while (p = get_line(f)) {
 			if (++ln < 2)
 				continue;
-			p = buffer;
-			while (isspace((unsigned int)*p))
-				p++;
 			n = strcspn(p, ": \t");
 			p[n]= '\0';
 			ifl = NULL;
@@ -479,7 +476,6 @@ discover_interfaces(int argc, char * const *argv)
 			}
 		}
 		fclose(f);
-		free(buffer);
 	}
 	return ifs;
 }

if-options.c

@@ -586,8 +586,7 @@ read_config(const char *file, const char *ifname)
 {
 	struct if_options *ifo;
 	FILE *f;
-	size_t len = 0;
-	char *line, *option, *p, *buffer = NULL;
+	char *line, *option, *p;
 	int skip = 0;
 
 	/* Seed our default options */
@@ -612,18 +611,8 @@ read_config(const char *file, const char *ifname)
 	if (!f)
 		return ifo;
 
-	while ((get_line(&buffer, &len, f))) {
-		line = buffer;
-		while ((option = strsep(&line, " \t")))
-			if (*option != '\0')
-				break;
-		if (!option || *option == '\0' || *option == '#')
-			continue;
-		/* Trim leading whitespace */
-		if (line) {
-			while (*line != '\0' && (*line == ' ' || *line == '\t'))
-				line++;
-		}
+	while ((line = get_line(f))) {
+		option = strsep(&line, " \t");
 		/* Trim trailing whitespace */
 		if (line && *line) {
 			p = line + strlen(line) - 1;
@@ -646,7 +635,6 @@ read_config(const char *file, const char *ifname)
 			break;
 		}
 	}
-	free(buffer);
 	fclose(f);
 
 	/* Terminate the encapsulated options */