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Code Issues Releases Wiki Activity

Use an LFSR to generate unpredictable IDs.

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This commit is contained in:
Michael Graff
1999-12-15 03:11:00 +00:00
parent 21cbbc3e83
commit 0a9fedafec
1 changed files with 33 additions and 60 deletions
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93
lib/dns/dispatch.c
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@@ -24,6 +24,7 @@
#include <isc/assertions.h>
#include <isc/error.h>
#include <isc/lfsr.h>
#include <isc/mem.h>
#include <isc/mutex.h>
#include <isc/socket.h>
@@ -87,7 +88,7 @@ struct dns_dispatch {
ISC_LIST(dns_dispentry_t) rq_handlers; /* request handler list */
ISC_LIST(dns_dispatchevent_t) rq_events; /* holder for rq events */
dns_tcpmsg_t tcpmsg; /* for tcp streams */
isc_int32_t qid_state; /* state generator info */
isc_lfsr_t qid_lfsr; /* state generator info */
unsigned int qid_hashsize; /* hash table size */
unsigned int qid_mask; /* mask for hash table */
dns_displist_t *qid_table; /* the table itself */
@@ -105,54 +106,37 @@ struct dns_dispatch {
/*
* statics.
*/
static dns_dispentry_t *
bucket_search(dns_dispatch_t *, isc_sockaddr_t *,
dns_messageid_t, unsigned int);
static dns_dispentry_t *bucket_search(dns_dispatch_t *, isc_sockaddr_t *,
dns_messageid_t, unsigned int);
static void destroy(dns_dispatch_t *);
static void udp_recv(isc_task_t *, isc_event_t *);
static void tcp_recv(isc_task_t *, isc_event_t *);
static inline void startrecv(dns_dispatch_t *);
static dns_messageid_t randomid(dns_dispatch_t *);
static unsigned int hash(dns_dispatch_t *, isc_sockaddr_t *, dns_messageid_t);
static void free_buffer(dns_dispatch_t *disp, void *buf, unsigned int len);
static void *allocate_buffer(dns_dispatch_t *disp, unsigned int len);
static inline void free_event(dns_dispatch_t *disp, dns_dispatchevent_t *ev);
static inline dns_dispatchevent_t *allocate_event(dns_dispatch_t *disp);
static void do_next_request(dns_dispatch_t *disp, dns_dispentry_t *resp);
static void do_next_response(dns_dispatch_t *disp, dns_dispentry_t *resp);
static void do_cancel(dns_dispatch_t *disp, dns_dispentry_t *resp);
static dns_dispentry_t *linear_first(dns_dispatch_t *disp);
static dns_dispentry_t *linear_next(dns_dispatch_t *disp,
dns_dispentry_t *resp);
static void
destroy(dns_dispatch_t *);
/*
* Return an unpredictable message ID.
*/
static inline dns_messageid_t
randomid(dns_dispatch_t *disp)
{
isc_uint32_t id;
static void
udp_recv(isc_task_t *, isc_event_t *);
id = isc_lfsr_generate(&disp->qid_lfsr);
static void
tcp_recv(isc_task_t *, isc_event_t *);
static void
startrecv(dns_dispatch_t *);
static dns_messageid_t
randomid(dns_dispatch_t *);
static unsigned int
hash(dns_dispatch_t *, isc_sockaddr_t *, dns_messageid_t);
static void
free_buffer(dns_dispatch_t *disp, void *buf, unsigned int len);
static void *
allocate_buffer(dns_dispatch_t *disp, unsigned int len);
static inline void
free_event(dns_dispatch_t *disp, dns_dispatchevent_t *ev);
static inline dns_dispatchevent_t *
allocate_event(dns_dispatch_t *disp);
static void
do_next_request(dns_dispatch_t *disp, dns_dispentry_t *resp);
static void
do_next_response(dns_dispatch_t *disp, dns_dispentry_t *resp);
static void
do_cancel(dns_dispatch_t *disp, dns_dispentry_t *resp);
static dns_dispentry_t *
linear_first(dns_dispatch_t *disp);
static dns_dispentry_t *
linear_next(dns_dispatch_t *disp, dns_dispentry_t *resp);
return ((dns_messageid_t)(id & 0x0000ffff));
}
static dns_dispentry_t *
linear_first(dns_dispatch_t *disp)
@@ -212,18 +196,6 @@ hash(dns_dispatch_t *disp, isc_sockaddr_t *dest, dns_messageid_t id)
return (ret);
}
/*
* Return a random message ID. For now this isn't too clever...
* XXXMLG
*/
static dns_messageid_t
randomid(dns_dispatch_t *disp)
{
disp->qid_state += 7;
return ((dns_messageid_t)disp->qid_state);
}
/*
* Called when refcount reaches 0 (and safe to destroy)
*/
@@ -919,9 +891,10 @@ dns_dispatch_create(isc_mem_t *mctx, isc_socket_t *sock, isc_task_t *task,
}
/*
* should initialize qid_state here XXXMLG
* Initialize to a 32-bit LFSR.
* x^31 + x^6 + x^4 + x^2 + x + 1
*/
disp->qid_state = (unsigned int)disp;
isc_lfsr_init(&disp->qid_lfsr, random(), 32, 0x80000057U);
disp->magic = DISPATCH_MAGIC;