Re: [BUG] IMAP hibernation fails on FreeBSD 15.x with "Invalid peer_dev_major value"

Hi Timo,
I tested your patch on FreeBSD 15.x and can confirm that it completely resolves the issue.
Test scenario:

1. Connected via telnet localhost 143, authenticated, selected INBOX, and issued A03 IDLE.
2. Verified via doveadm who that after the hibernation timeout, the session successfully transitioned from imap to imap-hibernate ([email protected] 1 imap-hibernate (PID) (127.0.0.1)).
3. Sent a test email from an external server — the hibernated session woke up instantly, received the real-time notification (* 4297 EXISTS), and returned to the imap service without dropping the connection.
4. Checked the system logs — no more Invalid peer_dev_major value errors.

Everything works as expected - tested it more than once to hibernate. Thanks for the fix! 
You can follow what happens with FreeBSD PR on https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=286695. It will be great if you can follow the thread.

KR,
Jordan

PS.

A02 SELECT INBOX
* FLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-1 unknown-2 unknown-4 unknown-8 unknown-5 unknown-7 unknown-3 unknown-10 $NotJunk NotJunk $Forwarded Forwarded $Junk Junk $label1 JunkRecorded $MailFlagBit0 NonJunk)
* OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-1 unknown-2 unknown-4 unknown-8 unknown-5 unknown-7 unknown-3 unknown-10 $NotJunk NotJunk $Forwarded Forwarded $Junk Junk $label1 JunkRecorded $MailFlagBit0 NonJunk \*)] Flags permitted.
* 4296 EXISTS
* 0 RECENT
* OK [UNSEEN 1] First unseen.
* OK [UIDVALIDITY 1610577026] UIDs valid
* OK [UIDNEXT 95301] Predicted next UID
* OK [HIGHESTMODSEQ 16189] Highest
A02 OK [READ-WRITE] Select completed (0.006 + 0.000 + 0.005 secs).
A03 IDLE
+ idling
* OK Still here
* OK Still here
* OK Still here
* OK Still here
* OK Still here
* OK Still here
* 4297 EXISTS
* 1 RECENT
* 4297 FETCH (FLAGS (\Recent $NotJunk NotJunk))
* OK Still here
* OK Still here
* OK Still here
* OK Still here
* OK Still here
* OK Still here

# doveadm who
username            # service (pids)           (ips)
[email protected] 3 imap    (4315 5394 3153) (46.10.221.52)
[email protected] 1 imap-hibernate (4351)           (127.0.0.1)

# doveadm who
username            # service (pids)                (ips)
[email protected] 4 imap    (4315 5632 5394 3153) (46.10.221.52 127.0.0.1)

and here it goes again to hibernate 2nd time:
# doveadm who
username            # service (pids)                (ips)
[email protected] 4 imap    (7247 6707 5999 3153) (46.10.221.52)
[email protected] 1 imap-hibernate (6686)                (127.0.0.1)


Telnet session never disconnected or frozen somehow.


# cat /usr/ports/mail/dovecot24/files/patch-src_imap_imap-client-hibernate.c
--- src/imap/imap-client-hibernate.c.orig	2026-08-05 21:51:45 UTC
+++ src/imap/imap-client-hibernate.c
@@ -62,7 +62,8 @@ static void imap_hibernate_write_cmd(struct client *cl
 	str_append_tabescaped(cmd, user->set->unexpanded_mail_log_prefix);
 	str_printfa(cmd, "\tidle_notify_interval=%u",
 		    client->set->imap_idle_notify_interval);
-	if (fstat(client->fd_in, &peer_st) == 0) {
+	if (fstat(client->fd_in, &peer_st) == 0 &&
+	    peer_st.st_dev != (dev_t)-1) {
 		str_printfa(cmd, "\tpeer_dev_major=%lu\tpeer_dev_minor=%lu\tpeer_ino=%llu",
 			    (unsigned long)major(peer_st.st_dev),
 			    (unsigned long)minor(peer_st.st_dev),



> On 6 Aug 2026, at 0:46, Jordan Ostrev <[email protected]> wrote:
> 
> Hi,
> 
> I'm not a kernel developer, but I checked how FreeBSD handles socket stats (soo_stat() in sys/kern/sys_socket.c). On FreeBSD, fstat() on a socket returns st_dev = NODEV and st_ino = 0. Since st_ino is always 0 for sockets, it isn't unique or usable for verification either.
> So your proposed patch to skip the entire check when st_dev == (dev_t)-1 is indeed the right approach.
> 
> KR,
> Jordan
> 
> 
>> On 5 Aug 2026, at 23:56, Timo Sirainen <[email protected]> wrote:
>> 
>> Hi,
>> 
>> I'm mainly wondering if the device is NODEV, is the inode still usable or is that also some 0 or -1? This is likely a simpler patch, but it also removes the inode check also, which isn't good if it would be usable:
>> 
>> diff --git a/src/imap/imap-client-hibernate.c b/src/imap/imap-client-hibernate.c
>> index cb640c3695..191b0cfef9 100644
>> --- a/src/imap/imap-client-hibernate.c
>> +++ b/src/imap/imap-client-hibernate.c
>> @@ -62,7 +62,10 @@ static void imap_hibernate_write_cmd(struct client *client, string_t *cmd,
>>        str_append_tabescaped(cmd, user->set->unexpanded_mail_log_prefix);
>>        str_printfa(cmd, "\tidle_notify_interval=%u",
>>                    client->set->imap_idle_notify_interval);
>> -       if (fstat(client->fd_in, &peer_st) == 0) {
>> +       /* e.g. FreeBSD returns NODEV as sockets' st_dev, which can't be
>> +          used for verifying that the fd is the expected one. */
>> +       if (fstat(client->fd_in, &peer_st) == 0 &&
>> +           peer_st.st_dev != (dev_t)-1) {
>>                str_printfa(cmd, "\tpeer_dev_major=%lu\tpeer_dev_minor=%lu\tpeer_ino=%llu",
>>                            (unsigned long)major(peer_st.st_dev),
>>                            (unsigned long)minor(peer_st.st_dev),
>

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