Use C99 like the Linux kernel, again

Apply to loop variables so that they don't leak out of the loop - unless
they leak on purpose.

src/ipv4.c

@@ -887,9 +887,7 @@ int ipv4_add_split_vpn_route(struct tunnel *tunnel, char *dest, char *mask,
 
 static int ipv4_set_split_routes(struct tunnel *tunnel)
 {
-	int i;
-
-	for (i = 0; i < tunnel->ipv4.split_routes; i++) {
+	for (int i = 0; i < tunnel->ipv4.split_routes; i++) {
 		struct rtentry *route;
 		int ret;
 
@@ -1056,9 +1054,7 @@ int ipv4_restore_routes(struct tunnel *tunnel)
 
 static inline char *replace_char(char *str, char find, char replace)
 {
-	int i;
-
-	for (i = 0; i < strlen(str); i++)
+	for (int i = 0; i < strlen(str); i++)
 		if (str[i] == find)
 			str[i] = replace;
 	return str;

src/ssl.h

@@ -130,13 +130,9 @@ static inline int handle_ssl_error(SSL *ssl, int ret)
  */
 static inline int safe_ssl_read(SSL *ssl, uint8_t *buf, int bufsize)
 {
-	int ret;
+	int ret = SSL_read(ssl, buf, bufsize);
 
-	ret = SSL_read(ssl, buf, bufsize);
-	if (ret > 0)
-		return ret;
-
-	return handle_ssl_error(ssl, ret);
+	return (ret > 0) ? ret : handle_ssl_error(ssl, ret);
 }
 
 /*
@@ -147,9 +143,7 @@ static inline int safe_ssl_read(SSL *ssl, uint8_t *buf, int bufsize)
  */
 static inline int safe_ssl_read_all(SSL *ssl, uint8_t *buf, int bufsize)
 {
-	int n = 0;
-
-	while (n < bufsize) {
+	for (int n = 0; n < bufsize; ) {
 		int ret;
 
 		ret = safe_ssl_read(ssl, &buf[n], bufsize - n);
@@ -175,13 +169,9 @@ static inline int safe_ssl_read_all(SSL *ssl, uint8_t *buf, int bufsize)
  */
 static inline int safe_ssl_write(SSL *ssl, const uint8_t *buf, int n)
 {
-	int ret;
-
-	ret = SSL_write(ssl, buf, n);
-	if (ret > 0)
-		return ret;
+	int ret = SSL_write(ssl, buf, n);
 
-	return handle_ssl_error(ssl, ret);
+	return (ret > 0) ? ret : handle_ssl_error(ssl, ret);
 }
 
 #endif