afb-session: Use ad-hoc pseudo-random uuid

The use of the generator given by the lib uuid
implies the use of the system call 'getrandom'
without the flag GRND_NONBLOCK. It has a weird
effect on boot because many binders require
the generation of uuid at the same time but
getrandom is subject to starving.

This introduced a tiny pseudo-random generation
of UUID that does not implies the use of 'getrandom'.

Bug-AGL: SPEC-1655

Change-Id: I5131072881d7a53f0edda9e36762985c96a04550
Signed-off-by: Jose Bollo <jose.bollo@iot.bzh>

diff --git a/src/afb-session.c b/src/afb-session.c
index adfed2a..fdc88fd 100644 (file)
--- a/src/afb-session.c
+++ b/src/afb-session.c
@@ -26,6 +26,7 @@
 #include <string.h>
 #include <uuid/uuid.h>
 #include <errno.h>
+#include <unistd.h>
 
 #include "afb-session.h"
 #include "afb-hook.h"
@@ -106,7 +107,56 @@ static inline time_t time_now()
 static void new_uuid(char uuid[SIZEUUID])
 {
        uuid_t newuuid;
+
+#if defined(USE_UUID_GENERATE)
        uuid_generate(newuuid);
+#else
+       struct timespec ts;
+       static uint16_t pid;
+       static uint16_t counter;
+       static char state[32];
+       static struct random_data rdata;
+
+       int32_t x;
+       clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
+       if (pid == 0) {
+               pid = (uint16_t)getpid();
+               counter = (uint16_t)(ts.tv_nsec >> 8);
+               rdata.state = NULL;
+               initstate_r((((unsigned)pid) << 16) + ((unsigned)counter),
+                                       state, sizeof state, &rdata);
+       }
+       ts.tv_nsec ^= (long)ts.tv_sec;
+       if (++counter == 0)
+               counter = 1;
+
+       newuuid[0] = (char)(ts.tv_nsec >> 24);
+       newuuid[1] = (char)(ts.tv_nsec >> 16);
+       newuuid[2] = (char)(ts.tv_nsec >> 8);
+       newuuid[3] = (char)(ts.tv_nsec);
+
+       newuuid[4] = (char)(pid >> 8);
+       newuuid[5] = (char)(pid);
+
+       random_r(&rdata, &x);
+       newuuid[6] = (char)(((x >> 16) & 0x0f) | 0x40); /* pseudo-random version */
+       newuuid[7] = (char)(x >> 8);
+
+       random_r(&rdata, &x);
+       newuuid[8] = (char)(((x >> 16) & 0x3f) | 0x80); /* variant RFC4122 */
+       newuuid[9] = (char)(x >> 8);
+
+       random_r(&rdata, &x);
+       newuuid[10] = (char)(x >> 16);
+       newuuid[11] = (char)(x >> 8);
+
+       random_r(&rdata, &x);
+       newuuid[12] = (char)(x >> 16);
+       newuuid[13] = (char)(x >> 8);
+
+       newuuid[14] = (char)(counter >> 8);
+       newuuid[15] = (char)(counter);
+#endif
        uuid_unparse_lower(newuuid, uuid);
 }