From 716ca530e1c4515d8683c9d5be3d56b301758b66 Mon Sep 17 00:00:00 2001
From: James <>
Date: Wed, 4 Nov 2015 11:49:21 +0000
Subject: trunk-47381

---
 .../uml/patches-4.1/102-pseudo-random-mac.patch    | 124 +++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 target/linux/uml/patches-4.1/102-pseudo-random-mac.patch

(limited to 'target/linux/uml/patches-4.1/102-pseudo-random-mac.patch')

diff --git a/target/linux/uml/patches-4.1/102-pseudo-random-mac.patch b/target/linux/uml/patches-4.1/102-pseudo-random-mac.patch
new file mode 100644
index 0000000..fc54f60
--- /dev/null
+++ b/target/linux/uml/patches-4.1/102-pseudo-random-mac.patch
@@ -0,0 +1,124 @@
+===============================================================================
+
+This patch makes MAC addresses of network interfaces predictable. In
+particular, it adds a small routine that computes MAC addresses of based on
+a SHA1 hash of the virtual machine name and interface ID.
+
+TECHNICAL INFORMATION:
+
+Applies to vanilla kernel 3.9.4.
+
+===============================================================================
+--- a/arch/um/Kconfig.net
++++ b/arch/um/Kconfig.net
+@@ -21,6 +21,19 @@ config UML_NET
+         enable at least one of the following transport options to actually
+         make use of UML networking.
+ 
++config UML_NET_RANDOM_MAC
++	bool "Use random MAC addresses for network interfaces"
++	default n
++	depends on UML_NET
++	help
++        Virtual network devices inside a User-Mode Linux instance must be
++        assigned a MAC (Ethernet) address. If none is specified on the UML
++        command line, one must be automatically computed. If this option is
++        enabled, a randomly generated address is used. Otherwise, if this
++        option is disabled, the address is generated from a SHA1 hash of
++        the umid of the UML instance and the interface name. The latter choice
++        is useful to make MAC addresses predictable.
++
+ config UML_NET_ETHERTAP
+ 	bool "Ethertap transport"
+ 	depends on UML_NET
+--- a/arch/um/drivers/net_kern.c
++++ b/arch/um/drivers/net_kern.c
+@@ -25,6 +25,13 @@
+ #include <net_kern.h>
+ #include <net_user.h>
+ 
++#include <crypto/sha.h>
++#include <linux/string.h>
++#include <linux/crypto.h>
++#include <linux/err.h>
++#include <linux/scatterlist.h>
++#include "os.h"
++
+ #define DRIVER_NAME "uml-netdev"
+ 
+ static DEFINE_SPINLOCK(opened_lock);
+@@ -295,11 +302,47 @@ static void uml_net_user_timer_expire(un
+ #endif
+ }
+ 
++#ifndef CONFIG_UML_NET_RANDOM_MAC
++
++/* Compute a SHA1 hash of the UML instance's id and
++ *  * an interface name. */
++static int compute_hash(const char *umid, const char *ifname, char *hash) {
++	char vmif[1024];
++	struct scatterlist sg;
++	struct crypto_hash *tfm;
++	struct hash_desc desc;
++
++	strcpy (vmif, umid);
++	strcat (vmif, ifname);
++
++	tfm = crypto_alloc_hash("sha1", 0, CRYPTO_ALG_ASYNC);
++	if (IS_ERR(tfm))
++		return 1;
++
++	desc.tfm = tfm;
++	desc.flags = 0;
++
++	sg_init_table(&sg, 1);
++	sg_set_buf(&sg, vmif, strlen(vmif));
++
++	if (crypto_hash_digest(&desc, &sg, strlen(vmif), hash)) {
++		crypto_free_hash(tfm);
++		return 1;
++	}
++
++	crypto_free_hash(tfm);
++
++	return 0;
++}
++
++#endif
++
+ static void setup_etheraddr(struct net_device *dev, char *str)
+ {
+ 	unsigned char *addr = dev->dev_addr;
+ 	char *end;
+ 	int i;
++	u8 hash[SHA1_DIGEST_SIZE];
+ 
+ 	if (str == NULL)
+ 		goto random;
+@@ -340,9 +383,26 @@ static void setup_etheraddr(struct net_d
+ 	return;
+ 
+ random:
++#ifdef CONFIG_UML_NET_RANDOM_MAC
+ 	printk(KERN_INFO
+ 	       "Choosing a random ethernet address for device %s\n", dev->name);
+ 	eth_hw_addr_random(dev);
++#else
++	printk(KERN_INFO
++	       "Computing a digest to use as ethernet address for device %s\n", dev->name);
++	if (compute_hash(get_umid(), dev->name, hash)) {
++		printk(KERN_WARNING
++		       "Could not compute digest to use as ethernet address for device %s. "
++		       "Using random address instead.\n", dev->name);
++		random_ether_addr(addr);
++	}
++	else {
++		for (i=0; i < 6; i++)
++			addr[i] = (hash[i] + hash[i+6]) % 0x100;
++	}
++	addr [0] &= 0xfe; /* clear multicast bit */
++	addr [0] |= 0x02; /* set local assignment bit (IEEE802) */
++#endif
+ }
+ 
+ static DEFINE_SPINLOCK(devices_lock);
-- 
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