dsync: Add per-mailbox sync lock that is always used. Both importing and exporting gets the lock before they even sync the mailbox. The lock is kept until the import/export finishes. This guarantees that no matter how dsync is run, two dsyncs can't be working on the same mailbox at the same time. This lock is in addition to the optional per-user lock enabled by the -l parameter. If the -l parameter is used, the same lock timeout is used for the per-mailbox lock. Otherwise 30s timeout is used. This should help to avoid email duplication when replication is enabled for public namespaces, and maybe in some other rare situations as well.

#ifndef MAIL_IP_H
#define MAIL_IP_H

extern struct mail_ip *stable_mail_ips;

struct mail_ip *mail_ip_login(const struct ip_addr *ip_addr);
void mail_ip_disconnected(struct mail_ip *ip);
struct mail_ip *mail_ip_lookup(const struct ip_addr *ip_addr);
void mail_ip_refresh(struct mail_ip *ip, const struct stats *diff_stats)
	ATTR_NULL(2);

void mail_ip_ref(struct mail_ip *ip);
void mail_ip_unref(struct mail_ip **ip);

void mail_ips_free_memory(void);
void mail_ips_init(void);
void mail_ips_deinit(void);

#endif