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9df86f997e
Maksim Kupriianov reported very strange crashes in fwrr_update_position() which didn't make sense because of an apparent divide overflow except that the value was not null in the core. It happens that while the locking is correct in all the functions' call graph, the uppermost one (fwrr_get_next_server()) incorrectly expected that its target server was already locked when called. This stupid assumption causd the server lock not to be held when calling the other ones, explaining how it was possible to change the server's eweight by calling srv_lb_commit_status() under the server lock yet collide with its unprotected usage. This commit makes sure that fwrr_get_server_from_group() retrieves a locked server and that fwrr_get_next_server() is responsible for unlocking the server before returning it. There is one subtlety in this function which is that it builds a list of avoided servers that were full while scanning the tree, and all of them are queued in a full state so they must be unlocked upon return. Many thanks to Maksim for providing detailed info allowing to narrow down this bug. This fix must be backported to 1.9. In 1.8 the lock seems much wider and changes to the server's state are performed under the rendez-vous point so this it doesn't seem possible that it happens there.
149 lines
4.1 KiB
C
149 lines
4.1 KiB
C
/*
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* include/proto/backend.h
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* Functions prototypes for the backend.
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*
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* Copyright (C) 2000-2012 Willy Tarreau - w@1wt.eu
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation, version 2.1
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* exclusively.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _PROTO_BACKEND_H
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#define _PROTO_BACKEND_H
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#include <common/config.h>
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#include <common/time.h>
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#include <types/backend.h>
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#include <types/proxy.h>
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#include <types/server.h>
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#include <types/stream.h>
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int assign_server(struct stream *s);
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int assign_server_address(struct stream *s, struct connection *srv_conn);
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int assign_server_and_queue(struct stream *s);
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int connect_server(struct stream *s);
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int srv_redispatch_connect(struct stream *t);
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const char *backend_lb_algo_str(int algo);
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int backend_parse_balance(const char **args, char **err, struct proxy *curproxy);
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int tcp_persist_rdp_cookie(struct stream *s, struct channel *req, int an_bit);
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int be_downtime(struct proxy *px);
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void recount_servers(struct proxy *px);
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void update_backend_weight(struct proxy *px);
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int be_lastsession(const struct proxy *be);
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/* Returns number of usable servers in backend */
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static inline int be_usable_srv(struct proxy *be)
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{
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if (be->state == PR_STSTOPPED)
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return 0;
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else if (be->srv_act)
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return be->srv_act;
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else if (be->lbprm.fbck)
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return 1;
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else
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return be->srv_bck;
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}
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/* set the time of last session on the backend */
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static inline void be_set_sess_last(struct proxy *be)
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{
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be->be_counters.last_sess = now.tv_sec;
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}
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/* This function returns non-zero if the designated server will be
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* usable for LB according to pending weight and state.
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* Otherwise it returns 0.
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*/
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static inline int srv_willbe_usable(const struct server *srv)
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{
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enum srv_state state = srv->next_state;
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if (!srv->next_eweight)
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return 0;
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if (srv->next_admin & SRV_ADMF_MAINT)
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return 0;
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if (srv->next_admin & SRV_ADMF_DRAIN)
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return 0;
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switch (state) {
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case SRV_ST_STARTING:
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case SRV_ST_RUNNING:
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return 1;
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case SRV_ST_STOPPING:
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case SRV_ST_STOPPED:
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return 0;
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}
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return 0;
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}
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/* This function returns non-zero if the designated server was usable for LB
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* according to its current weight and state. Otherwise it returns 0.
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*/
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static inline int srv_currently_usable(const struct server *srv)
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{
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enum srv_state state = srv->cur_state;
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if (!srv->cur_eweight)
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return 0;
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if (srv->cur_admin & SRV_ADMF_MAINT)
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return 0;
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if (srv->cur_admin & SRV_ADMF_DRAIN)
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return 0;
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switch (state) {
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case SRV_ST_STARTING:
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case SRV_ST_RUNNING:
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return 1;
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case SRV_ST_STOPPING:
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case SRV_ST_STOPPED:
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return 0;
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}
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return 0;
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}
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/* This function commits the next server state and weight onto the current
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* ones in order to detect future changes. The server's lock is expected to
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* be held when calling this function.
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*/
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static inline void srv_lb_commit_status(struct server *srv)
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{
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srv->cur_state = srv->next_state;
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srv->cur_admin = srv->next_admin;
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srv->cur_eweight = srv->next_eweight;
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}
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/* This function returns true when a server has experienced a change since last
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* commit on its state or weight, otherwise zero.
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*/
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static inline int srv_lb_status_changed(const struct server *srv)
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{
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return (srv->next_state != srv->cur_state ||
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srv->next_admin != srv->cur_admin ||
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srv->next_eweight != srv->cur_eweight);
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}
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/* sends a log message when a backend goes down, and also sets last
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* change date.
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*/
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void set_backend_down(struct proxy *be);
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#endif /* _PROTO_BACKEND_H */
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/*
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* Local variables:
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* c-indent-level: 8
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* c-basic-offset: 8
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* End:
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*/
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