target/linux/uml/patches-6.1/102-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/drivers/Kconfig
  13 +++ b/arch/um/drivers/Kconfig
  14 @@ -143,6 +143,20 @@ 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_DETERMINISTIC_MAC
  19 +       bool "Use deterministic MAC addresses for network interfaces"
  20 +       default y
  21 +       depends on UML_NET
  22 +       select CRYPTO_SHA1
  23 +       help
  24 +        Virtual network devices inside a User-Mode Linux instance must be
  25 +        assigned a MAC (Ethernet) address. If none is specified on the UML
  26 +        command line, one must be automatically computed. If this option is
  27 +        enabled, a randomly generated address is used. Otherwise, if this
  28 +        option is disabled, the address is generated from a SHA1 hash of
  29 +        the umid of the UML instance and the interface name. The latter choice
  30 +        is useful to make MAC addresses predictable.
  31 +
  32  config UML_NET_ETHERTAP
  33         bool "Ethertap transport (obsolete)"
  34         depends on UML_NET
  35 --- a/arch/um/drivers/net_kern.c
  36 +++ b/arch/um/drivers/net_kern.c
  37 @@ -25,6 +25,14 @@
  38  #include <net_kern.h>
  39  #include <net_user.h>
  40
  41 +#include <crypto/sha1.h>
  42 +#include <crypto/hash.h>
  43 +#include <linux/string.h>
  44 +#include <linux/crypto.h>
  45 +#include <linux/err.h>
  46 +#include <linux/scatterlist.h>
  47 +#include "os.h"
  48 +
  49  #define DRIVER_NAME "uml-netdev"
  50
  51  static DEFINE_SPINLOCK(opened_lock);
  52 @@ -274,9 +282,55 @@ static const struct ethtool_ops uml_net_
  53         .get_ts_info    = ethtool_op_get_ts_info,
  54  };
  55
  56 +#ifdef CONFIG_UML_NET_DETERMINISTIC_MAC
  57 +
  58 +/* Compute a SHA1 hash of the UML instance's id and
  59 + *  * an interface name. */
  60 +static int compute_hash(const char *umid, const char *ifname, char *hash)
  61 +{
  62 +       struct ahash_request *desc = NULL;
  63 +       struct crypto_ahash *tfm = NULL;
  64 +       struct scatterlist sg;
  65 +       char *vmif = NULL;
  66 +       int ret = -ENOMEM;
  67 +
  68 +       vmif = kmalloc(1024, GFP_KERNEL);
  69 +       if (!vmif)
  70 +               goto out;
  71 +
  72 +       strcpy (vmif, umid);
  73 +       strcat (vmif, ifname);
  74 +
  75 +       tfm = crypto_alloc_ahash("sha1", 0, CRYPTO_ALG_ASYNC);
  76 +       if (IS_ERR(tfm))
  77 +               goto out;
  78 +
  79 +       desc = ahash_request_alloc(tfm, GFP_KERNEL);
  80 +       if (!desc)
  81 +               goto out;
  82 +
  83 +       crypto_ahash_clear_flags(tfm, ~0);
  84 +
  85 +       sg_init_table(&sg, 1);
  86 +       sg_set_buf(&sg, vmif, strlen(vmif));
  87 +
  88 +       ahash_request_set_crypt(desc, &sg, hash, strlen(vmif));
  89 +
  90 +       ret = crypto_ahash_digest(desc);
  91 +out:
  92 +       crypto_free_ahash(tfm);
  93 +       ahash_request_free(desc);
  94 +       kfree(vmif);
  95 +
  96 +       return ret;
  97 +}
  98 +
  99 +#endif
 100 +
 101  void uml_net_setup_etheraddr(struct net_device *dev, char *str)
 102  {
 103         u8 addr[ETH_ALEN];
 104 +       u8 hash[SHA1_DIGEST_SIZE];
 105         char *end;
 106         int i;
 107
 108 @@ -320,9 +374,26 @@ void uml_net_setup_etheraddr(struct net_
 109         return;
 110
 111  random:
 112 +#ifndef CONFIG_UML_NET_DETERMINISTIC_MAC
 113         printk(KERN_INFO
 114                "Choosing a random ethernet address for device %s\n", dev->name);
 115         eth_hw_addr_random(dev);
 116 +#else
 117 +       printk(KERN_INFO
 118 +              "Computing a digest to use as ethernet address for device %s\n", dev->name);
 119 +       if (compute_hash(get_umid(), dev->name, hash) < 0) {
 120 +               printk(KERN_WARNING
 121 +                      "Could not compute digest to use as ethernet address for device %s. "
 122 +                      "Using random address instead.\n", dev->name);
 123 +               eth_random_addr(addr);
 124 +       }
 125 +       else {
 126 +               for (i=0; i < 6; i++)
 127 +                       addr[i] = (hash[i] + hash[i+6]) % 0x100;
 128 +       }
 129 +       addr [0] &= 0xfe; /* clear multicast bit */
 130 +       addr [0] |= 0x02; /* set local assignment bit (IEEE802) */
 131 +#endif
 132  }
 133
 134  static DEFINE_SPINLOCK(devices_lock);
 135 --- a/kernel/umh.c
 136 +++ b/kernel/umh.c
 137 @@ -357,12 +357,12 @@ static void helper_unlock(void)
 138  }
 139
 140  int call_usermodehelper_stdoutpipe(struct subprocess_info *sub_info,
 141 -                                       struct file **filp)
 142 +                                  struct file **filp)
 143  {
 144         struct file *f[2];
 145
 146         if (create_pipe_files(f, 0) < 0)
 147 -                return PTR_ERR(f);
 148 +               return PTR_ERR(f);
 149
 150         sub_info->stdout = f[1];
 151         *filp = f[0];