OpenWrt – Blame information for rev 4

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4 office 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 @@ -21,6 +21,19 @@ 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 @@ -295,11 +303,53 @@ 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 @@ -340,9 +390,26 @@ 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);