target/linux/uml/patches-4.14/102-pseudo-random-mac.patch

   1 ===============================================================================
   2
   3 This patch makes MAC addresses of network interfaces predictable. In
   4 particular, it adds a small routine that computes MAC addresses of based on
   5 a SHA1 hash of the virtual machine name and interface ID.
   6
   7 TECHNICAL INFORMATION:
   8
   9 Applies to vanilla kernel 3.9.4.
  10
  11 ===============================================================================
  12 --- a/arch/um/Kconfig.net
  13 +++ b/arch/um/Kconfig.net
  14 @@ -22,6 +22,19 @@ config UML_NET
  15          enable at least one of the following transport options to actually
  16          make use of UML networking.
  17
  18 +config UML_NET_RANDOM_MAC
  19 +       bool "Use random MAC addresses for network interfaces"
  20 +       default n
  21 +       depends on UML_NET
  22 +       help
  23 +        Virtual network devices inside a User-Mode Linux instance must be
  24 +        assigned a MAC (Ethernet) address. If none is specified on the UML
  25 +        command line, one must be automatically computed. If this option is
  26 +        enabled, a randomly generated address is used. Otherwise, if this
  27 +        option is disabled, the address is generated from a SHA1 hash of
  28 +        the umid of the UML instance and the interface name. The latter choice
  29 +        is useful to make MAC addresses predictable.
  30 +
  31  config UML_NET_ETHERTAP
  32         bool "Ethertap transport"
  33         depends on UML_NET
  34 --- a/arch/um/drivers/net_kern.c
  35 +++ b/arch/um/drivers/net_kern.c
  36 @@ -25,6 +25,14 @@
  37  #include <net_kern.h>
  38  #include <net_user.h>
  39
  40 +#include <crypto/sha.h>
  41 +#include <crypto/hash.h>
  42 +#include <linux/string.h>
  43 +#include <linux/crypto.h>
  44 +#include <linux/err.h>
  45 +#include <linux/scatterlist.h>
  46 +#include "os.h"
  47 +
  48  #define DRIVER_NAME "uml-netdev"
  49
  50  static DEFINE_SPINLOCK(opened_lock);
  51 @@ -288,11 +296,53 @@ static void uml_net_user_timer_expire(un
  52  #endif
  53  }
  54
  55 +#ifndef CONFIG_UML_NET_RANDOM_MAC
  56 +
  57 +/* Compute a SHA1 hash of the UML instance's id and
  58 + *  * an interface name. */
  59 +static int compute_hash(const char *umid, const char *ifname, char *hash)
  60 +{
  61 +       struct ahash_request *desc;
  62 +       struct crypto_ahash *tfm;
  63 +       struct scatterlist sg;
  64 +       char vmif[1024];
  65 +       int ret;
  66 +
  67 +       strcpy (vmif, umid);
  68 +       strcat (vmif, ifname);
  69 +
  70 +       tfm = crypto_alloc_ahash("sha1", 0, CRYPTO_ALG_ASYNC);
  71 +       if (IS_ERR(tfm))
  72 +               return -ENOMEM;
  73 +
  74 +       desc = ahash_request_alloc(tfm, GFP_KERNEL);
  75 +       if (!desc) {
  76 +               ret = -ENOMEM;
  77 +               goto out;
  78 +       }
  79 +
  80 +       crypto_ahash_clear_flags(tfm, ~0);
  81 +
  82 +       sg_init_table(&sg, 1);
  83 +       sg_set_buf(&sg, vmif, strlen(vmif));
  84 +
  85 +       ahash_request_set_crypt(desc, &sg, hash, strlen(vmif));
  86 +
  87 +       ret = crypto_ahash_digest(desc);
  88 +out:
  89 +       crypto_free_ahash(tfm);
  90 +
  91 +       return ret;
  92 +}
  93 +
  94 +#endif
  95 +
  96  static void setup_etheraddr(struct net_device *dev, char *str)
  97  {
  98         unsigned char *addr = dev->dev_addr;
  99         char *end;
 100         int i;
 101 +       u8 hash[SHA1_DIGEST_SIZE];
 102
 103         if (str == NULL)
 104                 goto random;
 105 @@ -333,9 +383,26 @@ static void setup_etheraddr(struct net_d
 106         return;
 107
 108  random:
 109 +#ifdef CONFIG_UML_NET_RANDOM_MAC
 110         printk(KERN_INFO
 111                "Choosing a random ethernet address for device %s\n", dev->name);
 112         eth_hw_addr_random(dev);
 113 +#else
 114 +       printk(KERN_INFO
 115 +              "Computing a digest to use as ethernet address for device %s\n", dev->name);
 116 +       if (compute_hash(get_umid(), dev->name, hash) < 0) {
 117 +               printk(KERN_WARNING
 118 +                      "Could not compute digest to use as ethernet address for device %s. "
 119 +                      "Using random address instead.\n", dev->name);
 120 +               random_ether_addr(addr);
 121 +       }
 122 +       else {
 123 +               for (i=0; i < 6; i++)
 124 +                       addr[i] = (hash[i] + hash[i+6]) % 0x100;
 125 +       }
 126 +       addr [0] &= 0xfe; /* clear multicast bit */
 127 +       addr [0] |= 0x02; /* set local assignment bit (IEEE802) */
 128 +#endif
 129  }
 130
 131  static DEFINE_SPINLOCK(devices_lock);