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Fix rib generation count for fib algo.

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Currently, PCB caching mechanism relies on the rib generation
 counter (rnh_gen) to invalidate cached nhops/LLE entries.

With certain fib algorithms, it is now possible that the
 datapath lookup state applies RIB changes with some delay.
In that scenario, PCB cache will invalidate on the RIB change,
 but the new lookup may result in the same nexthop being returned.
When fib algo finally gets in sync with the RIB changes, PCB cache
 will not receive any notification and will end up caching the stale data.

To fix this, introduce additional counter, rnh_gen_rib, which is used
 only when FIB_ALGO is enabled.
This counter is incremented by the control plane. Each time when fib algo
 synchronises with the RIB, it updates rnh_gen to the current rnh_gen_rib value.

Differential Revision: https://reviews.freebsd.org/D29812
Reviewed by:	donner
MFC after:	2 weeks
This commit is contained in:
Alexander V. Chernikov 2021-04-17 18:58:12 +00:00
parent 8ef97d2ba3
commit 33cb3cb2e3
3 changed files with 29 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
sys/net/route/fib_algo.c
View File

@ -525,6 +525,13 @@ schedule_fd_rebuild(struct fib_data *fd, const char *reason)
}
}
static void
sync_rib_gen(struct fib_data *fd)
{
FD_PRINTF(LOG_DEBUG, fd, "Sync gen %u -> %u", fd->fd_rh->rnh_gen, fd->fd_rh->rnh_gen_rib);
fd->fd_rh->rnh_gen = fd->fd_rh->rnh_gen_rib;
}
static int64_t
get_tv_diff_ms(const struct timeval *old_tv, const struct timeval *new_tv)
{
@ -680,6 +687,7 @@ apply_rtable_changes(struct fib_data *fd)
result = fd->fd_flm->flm_change_rib_items_cb(fd->fd_rh, q, fd->fd_algo_data);
if (result == FLM_SUCCESS) {
sync_rib_gen(fd);
for (int i = 0; i < q->count; i++)
if (q->entries[i].nh_old)
fib_unref_nhop(fd, q->entries[i].nh_old);
@ -811,6 +819,7 @@ handle_rtable_change_cb(struct rib_head *rnh, struct rib_cmd_info *rc,
switch (result) {
case FLM_SUCCESS:
sync_rib_gen(fd);
/* Unref old nexthop on success */
if (rc->rc_nh_old != NULL)
fib_unref_nhop(fd, rc->rc_nh_old);
@ -1236,7 +1245,9 @@ setup_fd_instance(struct fib_lookup_module *flm, struct rib_head *rh,
result = try_setup_fd_instance(flm, rh, prev_fd, &new_fd);
if ((result == FLM_SUCCESS) && attach) {
if (!fib_set_datapath_ptr(new_fd, &new_fd->fd_dp))
if (fib_set_datapath_ptr(new_fd, &new_fd->fd_dp))
sync_rib_gen(new_fd);
else
result = FLM_REBUILD;
}

6
sys/net/route/route_ctl.c
View File

@ -808,7 +808,7 @@ rt_unlinkrte(struct rib_head *rnh, struct rt_addrinfo *info, struct rib_cmd_info
rt->rte_flags &= ~RTF_UP;
/* Finalize notification */
rnh->rnh_gen++;
rib_bump_gen(rnh);
rnh->rnh_prefixes--;
rc->rc_cmd = RTM_DELETE;
@ -1060,7 +1060,7 @@ add_route_nhop(struct rib_head *rnh, struct rtentry *rt,
tmproutes_update(rnh, rt);
/* Finalize notification */
rnh->rnh_gen++;
rib_bump_gen(rnh);
rnh->rnh_prefixes++;
rc->rc_cmd = RTM_ADD;
@ -1116,7 +1116,7 @@ change_route_nhop(struct rib_head *rnh, struct rtentry *rt,
}
/* Finalize notification */
rnh->rnh_gen++;
rib_bump_gen(rnh);
if (rnd->rnd_nhop == NULL)
rnh->rnh_prefixes--;

15
sys/net/route/route_var.h
View File

@ -60,7 +60,7 @@ struct rib_head {
rn_walktree_t *rnh_walktree; /* traverse tree */
rn_walktree_from_t *rnh_walktree_from; /* traverse tree below a */
rnh_preadd_entry_f_t *rnh_preadd; /* hook to alter record prior to insertion */
rt_gen_t rnh_gen; /* generation counter */
rt_gen_t rnh_gen; /* datapath generation counter */
int rnh_multipath; /* multipath capable ? */
struct radix_node rnh_nodes[3]; /* empty tree for common case */
struct rmlock rib_lock; /* config/data path lock */
@ -71,6 +71,9 @@ struct rib_head {
struct callout expire_callout; /* Callout for expiring dynamic routes */
time_t next_expire; /* Next expire run ts */
uint32_t rnh_prefixes; /* Number of prefixes */
#ifdef FIB_ALGO
rt_gen_t rnh_gen_rib; /* rib generation counter */
#endif
uint32_t rib_dying:1; /* rib is detaching */
uint32_t rib_algo_fixed:1;/* fixed algorithm */
struct nh_control *nh_control; /* nexthop subsystem data */
@ -116,6 +119,16 @@ CHK_STRUCT_ROUTE_FIELDS(_ro_new); \
_Static_assert(__offsetof(struct route, ro_dst) == __offsetof(_ro_new, _dst_new),\
"ro_dst and " #_dst_new " are at different offset")
static inline void
rib_bump_gen(struct rib_head *rnh)
{
#ifdef FIB_ALGO
rnh->rnh_gen_rib++;
#else
rnh->rnh_gen++;
#endif
}
struct rib_head *rt_tables_get_rnh(uint32_t table, sa_family_t family);
int rt_getifa_fib(struct rt_addrinfo *info, u_int fibnum);
struct rib_cmd_info;