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place a limit on pipelined queries that can be processed simultaneously

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when the TCPDNS_CLIENTS_PER_CONN limit has been exceeded for a TCP
DNS connection, switch to sequential mode to ensure that memory cannot
be exhausted by too many simultaneous queries.
This commit is contained in:
Evan Hunt
2019-11-08 10:52:49 -08:00
parent 20bb812148
commit 123ee350dc
6 changed files with 235 additions and 88 deletions
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48
lib/isc/netmgr/netmgr-int.h
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@@ -89,8 +89,8 @@ struct isc_nmhandle {
isc_sockaddr_t peer;
isc_sockaddr_t local;
isc_nm_opaquecb doreset; /* reset extra callback, external */
isc_nm_opaquecb dofree; /* free extra callback, external */
isc_nm_opaquecb_t doreset; /* reset extra callback, external */
isc_nm_opaquecb_t dofree; /* free extra callback, external */
void * opaque;
char extra[];
};
@@ -312,15 +312,28 @@ struct isc_nmsocket {
isc_refcount_t references;
/*%
* TCPDNS socket is not pipelining.
* TCPDNS socket has been set not to pipeliine.
*/
atomic_bool sequential;
/*%
* TCPDNS socket has exceeded the maximum number of
* simultaneous requests per connecton, so will be temporarily
* restricted from pipelining.
*/
atomic_bool overlimit;
/*%
* TCPDNS socket in sequential mode is currently processing a packet,
* we need to wait until it finishes.
*/
atomic_bool processing;
/*%
* A TCP socket has had isc_nm_pauseread() called.
*/
atomic_bool readpaused;
/*%
* 'spare' handles for that can be reused to avoid allocations,
* for UDP.
@@ -334,24 +347,26 @@ struct isc_nmsocket {
/*%
* List of active handles.
* ah_size - size of ah_frees and ah_handles
* ah_cpos - current position in ah_frees;
* ah_handles - array of *handles.
* ah - current position in 'ah_frees'; this represents the
* current number of active handles;
* ah_size - size of the 'ah_frees' and 'ah_handles' arrays
* ah_handles - array pointers to active handles
*
* Adding a handle
* - if ah_cpos == ah_size, realloc
* - x = ah_frees[ah_cpos]
* - ah_frees[ah_cpos++] = 0;
* - if ah == ah_size, reallocate
* - x = ah_frees[ah]
* - ah_frees[ah++] = 0;
* - ah_handles[x] = handle
* - x must be stored with the handle!
* Removing a handle:
* - ah_frees[--ah_cpos] = x
* - ah_frees[--ah] = x
* - ah_handles[x] = NULL;
*
* XXXWPK for now this is locked with socket->lock, but we might want
* to change it to something lockless
* XXXWPK for now this is locked with socket->lock, but we
* might want to change it to something lockless
*/
size_t ah;
size_t ah_size;
size_t ah_cpos;
size_t *ah_frees;
isc_nmhandle_t **ah_handles;
@@ -360,6 +375,13 @@ struct isc_nmsocket {
size_t buf_len;
unsigned char *buf;
/*
* This function will be called with handle->sock
* as the argument whenever a handle's references drop
* to zero, after its reset callback has been called.
*/
isc_nm_opaquecb_t closehandle_cb;
isc__nm_readcb_t rcb;
void *rcbarg;
};