Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752463AbXJUDGy (ORCPT ); Sat, 20 Oct 2007 23:06:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751118AbXJUDGs (ORCPT ); Sat, 20 Oct 2007 23:06:48 -0400 Received: from mail.gmx.net ([213.165.64.20]:36306 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751110AbXJUDGr (ORCPT ); Sat, 20 Oct 2007 23:06:47 -0400 X-Authenticated: #1045983 X-Provags-ID: V01U2FsdGVkX18WpbU4870WUfJMli7B/X15gcfPg9IL3CHocUBtSQ 33XJycmw9F7wT+ From: Helge Deller To: Andrew Morton Subject: [PATCH 2/2] UUID: Time-based RFC 4122 UUID generator Date: Sat, 20 Oct 2007 22:00:03 +0200 User-Agent: KMail/1.9.7 Cc: linux-kernel@vger.kernel.org, Valdis.Kletnieks@vt.edu References: <200710202139.25595.deller@gmx.de> In-Reply-To: <200710202139.25595.deller@gmx.de> X-Face: &[jmHH-Dw>Aj):"[/t-VasJu+(5eP`/LEckV7V"JV,!nBy[6(/?#8M>x`5xzg/7:FkM.l@=?utf-8?q?=0A=0913?=<&9'nfV3"OkD~P)@j{P2=(uB7J(){:CcrM2jZeA+IBq?FUTp3c8Y{t+k<95mZf~[v"=?utf-8?q?=27=3A=0A=09t?="f6wKtHUPFB&/]Z5^?9~IQs=16R;Pg"NS9JD=DK!ft&4b@=?utf-8?q?S=7E=26q/MfI3=3BqWqlg7Q1=3D=3DjS4=0A=099V5OJkm=24WQ=5Bdc=5E=5FY?= =?utf-8?q?=27=5DDvibvMjizUZ=5D+=27Jd4UnM?=> X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8145 Lines: 259 The current Linux kernel currently contains the generate_random_uuid() function, which creates - based on RFC 4122 - truly random UUIDs and provides them to userspace through /proc/sys/kernel/random/boot_id and /proc/sys/kernel/random/uuid. The attached patch additionally adds the "Time-based UUID" variant of RFC 4122 to the Linux Kernel. With this patch applied, userspace applications may easily get real unique time-based UUIDs through /proc/sys/kernel/random/uuid_time. The attached implementation uses getnstimeofday() to get more fine-grained granularity than what would be possible with gettimeofday() in userspace. As such it's in principle possible to provide a lot more UUIDs (if needed) per time than in userspace. Additionally a mutex takes care of the proper locking against a mistaken double creation of UUIDs for simultanious running processes. Signed-off-by: Helge Deller CC: Valdis.Kletnieks@vt.edu drivers/char/random.c | 160 +++++++++++++++++++++++++++++++++++++++++++------ include/linux/sysctl.h | 5 - 2 files changed, 145 insertions(+), 20 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 1756b1f..3d6b6e0 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -239,6 +239,7 @@ #include #include #include +#include #include #include @@ -1174,12 +1177,134 @@ EXPORT_SYMBOL(generate_random_uuid); static int min_read_thresh = 8, min_write_thresh; static int max_read_thresh = INPUT_POOL_WORDS * 32; static int max_write_thresh = INPUT_POOL_WORDS * 32; -static char sysctl_bootid[16]; +static unsigned char sysctl_bootid[16] __read_mostly; /* - * These functions is used to return both the bootid UUID, and random - * UUID. The difference is in whether table->data is NULL; if it is, - * then a new UUID is generated and returned to the user. + * Generate time based UUID (RFC 4122) + * + * This function is protected with a mutex to ensure system-wide + * uniqiness of the new time based UUID. + */ +static void generate_random_uuid_time(unsigned char uuid_out[16]) +{ + static DEFINE_MUTEX(uuid_mutex); + static u64 last_time_all; + static u16 clock_seq, clock_seq_started; + static unsigned char last_mac[ETH_ALEN]; + static int clock_seq_initialized __read_mostly; + + struct timespec ts; + u64 time_all; + struct net_device *d; + int netdev_found = 0; + + mutex_lock(&uuid_mutex); + + /* Determine 60-bit timestamp value. For UUID version 1, this is + * represented by Coordinated Universal Time (UTC) as a count of 100- + * nanosecond intervals since 00:00:00.00, 15 October 1582 (the date of + * Gregorian reform to the Christian calendar). + */ +try_again: + getnstimeofday(&ts); + time_all = ((u64) ts.tv_sec) * (NSEC_PER_SEC/100); + time_all += ts.tv_nsec / 100; + + /* add offset from Gregorian Calendar to Jan 1 1970 */ + time_all += 12219292800000ULL * (NSEC_PER_MSEC/100); + time_all &= 0x0fffffffffffffffULL; /* limit to 60 bits */ + uuid_out[3] = (u8) time_all; + uuid_out[2] = (u8) (time_all >> 8); + uuid_out[1] = (u8) (time_all >> 16); + uuid_out[0] = (u8) (time_all >> 24); + uuid_out[5] = (u8) (time_all >> 32); + uuid_out[4] = (u8) (time_all >> 40); + uuid_out[7] = (u8) (time_all >> 48); + uuid_out[6] = (u8) (time_all >> 56); + + /* Determine clock sequence (max. 14 bit) */ + if (unlikely(!clock_seq_initialized)) { + get_random_bytes(&clock_seq, sizeof(clock_seq)); + clock_seq &= 0x3fff; + clock_seq_started = clock_seq; + clock_seq_initialized = 1; + } else { + if (unlikely(time_all <= last_time_all)) { +inc_clock_seq: clock_seq = (clock_seq+1) & 0x3fff; + if (unlikely(clock_seq == clock_seq_started)) { + clock_seq = (clock_seq-1) & 0x3fff; + goto try_again; /* wait until time advanced */ + } + } else + clock_seq_started = clock_seq; + } + last_time_all = time_all; + + uuid_out[8] = clock_seq >> 8; + uuid_out[9] = clock_seq & 0xff; + + /* Set the spatially unique node identifier */ +#ifdef CONFIG_NET + read_lock(&dev_base_lock); + for_each_netdev(&init_net, d) { + if (d->type == ARPHRD_ETHER && d->addr_len == ETH_ALEN + && d != init_net.loopback_dev) { + memcpy(&uuid_out[10], d->dev_addr, ETH_ALEN); + netdev_found = 1; + break; + } + } + read_unlock(&dev_base_lock); +#endif + if (unlikely(!netdev_found)) { + /* use bootid's nodeID if no network interface found */ + if (sysctl_bootid[8] == 0) + generate_random_uuid(sysctl_bootid); + memcpy(&uuid_out[10], &sysctl_bootid[10], ETH_ALEN); + } + /* if MAC/NodeID changed, create a new clock_seq value */ + if (unlikely(memcmp(&uuid_out[10], &last_mac, ETH_ALEN))) { + memcpy(&last_mac, &uuid_out[10], ETH_ALEN); + /* for very first UUID, do not increment clock_seq */ + if (unlikely(clock_seq_initialized == 1)) + clock_seq_initialized = 2; + else + goto inc_clock_seq; + } + + /* Set UUID version to 1 --- time-based generation */ + uuid_out[6] = (uuid_out[6] & 0x0F) | 0x10; + /* Set the UUID variant to DCE */ + uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80; + + mutex_unlock(&uuid_mutex); +} + + +/* + * Get UUID based on requested type. + */ +static unsigned char *get_uuid(void *extra1, unsigned char *uuid) +{ + switch ((int) extra1) { + case RANDOM_BOOT_ID: + uuid = sysctl_bootid; + if (unlikely(uuid[8] == 0)) + generate_random_uuid(uuid); + break; + case RANDOM_UUID: + generate_random_uuid(uuid); + break; + case RANDOM_UUID_TIME: + generate_random_uuid_time(uuid); + break; + } + return uuid; +} + +/* + * These functions are used to return the bootid UUID, random UUID and + * time based UUID. * * If the user accesses this via the proc interface, it will be returned * as an ASCII string in the standard UUID format. If accesses via the @@ -1191,13 +1316,13 @@ static int proc_do_uuid(ctl_table *table, int write, struct file *filp, ctl_table fake_table; unsigned char buf[64], tmp_uuid[16], *uuid; - uuid = table->data; - if (!uuid) { - uuid = tmp_uuid; - uuid[8] = 0; + /* random/time UUIDs need to be read completely at once */ + if ((int)table->extra1 != RANDOM_BOOT_ID && *ppos > 0) { + *lenp = 0; + return 0; } - if (uuid[8] == 0) - generate_random_uuid(uuid); + + uuid = get_uuid(table->extra1, tmp_uuid); sprintf(buf, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-" "%02x%02x%02x%02x%02x%02x", @@ -1221,13 +1346,7 @@ static int uuid_strategy(ctl_table *table, int __user *name, int nlen, if (!oldval || !oldlenp) return 1; - uuid = table->data; - if (!uuid) { - uuid = tmp_uuid; - uuid[8] = 0; - } - if (uuid[8] == 0) - generate_random_uuid(uuid); + uuid = get_uuid(table->extra1, tmp_uuid); if (get_user(len, oldlenp)) return -EFAULT; @@ -1284,11 +1403,11 @@ ctl_table random_table[] = { { .ctl_name = RANDOM_BOOT_ID, .procname = "boot_id", - .data = &sysctl_bootid, .maxlen = 16, .mode = 0444, .proc_handler = &proc_do_uuid, .strategy = &uuid_strategy, + .extra1 = (void *) RANDOM_BOOT_ID, }, { .ctl_name = RANDOM_UUID, @@ -1297,6 +1416,13 @@ ctl_table random_table[] = { .mode = 0444, .proc_handler = &proc_do_uuid, .strategy = &uuid_strategy, + .extra1 = (void *) RANDOM_UUID, + }, + { + .procname = "uuid_time", + .mode = 0444, + .proc_handler = &proc_do_uuid, + .extra1 = (void *) RANDOM_UUID_TIME, }, { .ctl_name = 0 } }; diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index e99171f..dd09d97 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -248,8 +248,9 @@ enum RANDOM_ENTROPY_COUNT=2, RANDOM_READ_THRESH=3, RANDOM_WRITE_THRESH=4, - RANDOM_BOOT_ID=5, - RANDOM_UUID=6 + RANDOM_BOOT_ID=5, /* rfc4122 version 4, boot UUID */ + RANDOM_UUID=6, /* rfc4122 version 4, random-based */ + RANDOM_UUID_TIME=7 /* rfc4122 version 1, time-based */ }; /* /proc/sys/kernel/pty */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/