From 966e9f1fc82662e4f9c330200490c121dacbd7c8 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Sun, 3 Sep 2017 20:37:21 +0200
Subject: [PATCH] network: remove allocation from lxc_mkifname()

lxc_mkifname() really doesn't need to allocate any memory.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
 src/lxc/criu.c         |  8 ++------
 src/lxc/lxc_user_nic.c | 13 +++++--------
 src/lxc/network.c      | 42 +++++++++++++++++-------------------------
 src/lxc/network.h      |  2 +-
 4 files changed, 25 insertions(+), 40 deletions(-)

diff --git a/src/lxc/criu.c b/src/lxc/criu.c
index 2f444ec44..9305b52a0 100644
--- a/src/lxc/criu.c
+++ b/src/lxc/criu.c
@@ -767,14 +767,10 @@ static bool restore_net_info(struct lxc_container *c)
 
 		if (netdev->priv.veth_attr.pair[0] == '\0' &&
 		    netdev->priv.veth_attr.veth1[0] == '\0') {
-			char *tmp;
-
-			tmp = lxc_mkifname(template);
-			if (!tmp)
+			if (!lxc_mkifname(template))
 				goto out_unlock;
 
-			strcpy(netdev->priv.veth_attr.veth1, tmp);
-			free(tmp);
+			strcpy(netdev->priv.veth_attr.veth1, template);
 		}
 	}
 
diff --git a/src/lxc/lxc_user_nic.c b/src/lxc/lxc_user_nic.c
index 6920c5462..9026bc425 100644
--- a/src/lxc/lxc_user_nic.c
+++ b/src/lxc/lxc_user_nic.c
@@ -566,23 +566,20 @@ out_del:
 static char *get_new_nicname(char *br, int pid, char **cnic)
 {
 	int ret;
-	char *nicname;
-	char template[IFNAMSIZ];
+	char nicname[IFNAMSIZ];
 
-	ret = snprintf(template, sizeof(template), "vethXXXXXX");
-	if (ret < 0 || (size_t)ret >= sizeof(template))
+	ret = snprintf(nicname, sizeof(nicname), "vethXXXXXX");
+	if (ret < 0 || (size_t)ret >= sizeof(nicname))
 		return NULL;
 
-	nicname = lxc_mkifname(template);
-	if (!nicname)
+	if (!lxc_mkifname(nicname))
 		return NULL;
 
 	if (!create_nic(nicname, br, pid, cnic)) {
-		free(nicname);
 		return NULL;
 	}
 
-	return nicname;
+	return strdup(nicname);
 }
 
 struct entry_line {
diff --git a/src/lxc/network.c b/src/lxc/network.c
index 1126cdec3..d2247273c 100644
--- a/src/lxc/network.c
+++ b/src/lxc/network.c
@@ -218,9 +218,6 @@ static int instantiate_veth(struct lxc_handler *handler, struct lxc_netdev *netd
 out_delete:
 	if (netdev->ifindex != 0)
 		lxc_netdev_delete_by_name(veth1);
-	if (netdev->priv.veth_attr.pair != veth1)
-		free(veth1);
-	free(veth2);
 	return -1;
 }
 
@@ -247,29 +244,29 @@ static int instantiate_macvlan(struct lxc_handler *handler, struct lxc_netdev *n
 	if (err) {
 		ERROR("Failed to create macvlan interface \"%s\" on \"%s\": %s",
 		      peer, netdev->link, strerror(-err));
-		goto out;
+		goto on_error;
 	}
 
 	netdev->ifindex = if_nametoindex(peer);
 	if (!netdev->ifindex) {
 		ERROR("Failed to retrieve ifindex for \"%s\"", peer);
-		goto out;
+		goto on_error;
 	}
 
 	if (netdev->upscript) {
 		err = run_script(handler->name, "net", netdev->upscript, "up",
 				 "macvlan", netdev->link, (char*) NULL);
 		if (err)
-			goto out;
+			goto on_error;
 	}
 
 	DEBUG("Instantiated macvlan \"%s\" with ifindex is %d and mode %d",
 	      peer, netdev->ifindex, netdev->priv.macvlan_attr.mode);
 
 	return 0;
-out:
+
+on_error:
 	lxc_netdev_delete_by_name(peer);
-	free(peer);
 	return -1;
 }
 
@@ -1918,14 +1915,14 @@ const char *lxc_net_type_to_str(int type)
 
 static const char padchar[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
-char *lxc_mkifname(const char *template)
+char *lxc_mkifname(char *template)
 {
-	int ifexists = 0;
-	size_t i = 0;
-	char *name = NULL;
 	unsigned int seed;
 	FILE *urandom;
 	struct ifaddrs *ifa, *ifaddr;
+	char name[IFNAMSIZ];
+	bool exists = false;
+	size_t i = 0;
 
 	if (strlen(template) >= IFNAMSIZ)
 		return NULL;
@@ -1949,17 +1946,14 @@ char *lxc_mkifname(const char *template)
 
 	/* Generate random names until we find one that doesn't exist. */
 	while (true) {
-		ifexists = 0;
-		name = strdup(template);
-
-		if (name == NULL)
-			return NULL;
+		name[0] = '\0';
+		strcpy(name, template);
 
+		exists = false;
 		for (i = 0; i < strlen(name); i++) {
 			if (name[i] == 'X') {
 #ifdef HAVE_RAND_R
-				name[i] = padchar[rand_r(&seed) %
-						  (strlen(padchar) - 1)];
+				name[i] = padchar[rand_r(&seed) % (strlen(padchar) - 1)];
 #else
 				name[i] = padchar[rand() % (strlen(padchar) - 1)];
 #endif
@@ -1967,20 +1961,18 @@ char *lxc_mkifname(const char *template)
 		}
 
 		for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
-			if (strcmp(ifa->ifa_name, name) == 0) {
-				ifexists = 1;
+			if (!strcmp(ifa->ifa_name, name)) {
+				exists = true;
 				break;
 			}
 		}
 
-		if (ifexists == 0)
+		if (!exists)
 			break;
-
-		free(name);
 	}
 
 	freeifaddrs(ifaddr);
-	return name;
+	return strcpy(template, name);
 }
 
 int setup_private_host_hw_addr(char *veth1)
diff --git a/src/lxc/network.h b/src/lxc/network.h
index fe127734f..833bfe6f3 100644
--- a/src/lxc/network.h
+++ b/src/lxc/network.h
@@ -256,7 +256,7 @@ extern int lxc_neigh_proxy_off(const char *name, int family);
 /* Generate a new unique network interface name.
  * Allocated memory must be freed by caller.
  */
-extern char *lxc_mkifname(const char *template);
+extern char *lxc_mkifname(char *template);
 
 extern const char *lxc_net_type_to_str(int type);
 extern int setup_private_host_hw_addr(char *veth1);