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syslogd: Handle DNS lookup of unknown remote hosts in domark()

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Refactor of nslookup of unknown remote syslog servers, both when
(re)reading the .conf file and at runtime.  This means we retry
DNS lookup every 30 sec, or INET_SUSPEND_TIME +/- 30 sec.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
This commit is contained in:
Joachim Nilsson 2019-11-29 10:25:19 +01:00
parent 90dd1b1c37
commit 0a8cecfa84
1 changed files with 45 additions and 45 deletions
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90
src/syslogd.c
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@ -1407,35 +1407,8 @@ void fprintlog_write(struct filed *f, struct iovec *iov, int iovcnt, int flags)
}
break;
/*
* The trick is to wait some time, then retry to get the
* address. If that fails retry x times and then give up.
*
* You'll run into this problem mostly if the name server you
* need for resolving the address is on the same machine, but
* is started after syslogd.
*/
case F_FORW_UNKN:
logit(" %s:%s\n", f->f_un.f_forw.f_hname, f->f_un.f_forw.f_serv);
fwd_suspend = time(NULL) - f->f_time;
if (fwd_suspend >= INET_SUSPEND_TIME) {
char *host = f->f_un.f_forw.f_hname;
char *serv = f->f_un.f_forw.f_serv;
logit("Forwarding suspension to %s:%s over, retrying\n", host, serv);
err = nslookup(host, serv, &ai);
if (err) {
WARN("Failure resolving %s:%s: %s", host, serv, gai_strerror(err));
} else {
NOTE("Found %s, resuming operation.", host);
f->f_un.f_forw.f_addr = ai;
f->f_prevcount = 0;
f->f_type = F_FORW;
goto f_forw;
}
} else
logit("Forwarding suspension not over, time left: %d\n",
(int)(INET_SUSPEND_TIME - fwd_suspend));
/* nslookup retry handled by domark() timer */
break;
case F_FORW:
@ -1931,6 +1904,43 @@ void flog(int pri, char *fmt, ...)
logmsg(&buffer);
}
static void forw_lookup(struct filed *f)
{
struct addrinfo *ai;
time_t diff;
char *host = f->f_un.f_forw.f_hname;
char *serv = f->f_un.f_forw.f_serv;
int err, init;
/* Called from cfline() for initial lookup? */
init = f->f_type == F_UNUSED ? 1 : 0;
diff = now - f->f_time;
if (!init && diff < INET_SUSPEND_TIME) {
logit("Forwarding suspension not over, time left: %d\n",
(int)(INET_SUSPEND_TIME - diff));
return;
}
if (!init)
logit("Forwarding suspension to %s:%s over, retrying\n", host, serv);
err = nslookup(host, serv, &ai);
if (err) {
WARN("Failed resolving '%s:%s': %s", host, serv, gai_strerror(err));
f->f_type = F_FORW_UNKN;
f->f_time = now;
return;
}
if (!init)
NOTE("Successfully resolved '%s:%s', resuming operation.", host, serv);
f->f_type = F_FORW;
f->f_un.f_forw.f_addr = ai;
f->f_prevcount = 0;
}
void domark(int signo)
{
struct filed *f;
@ -1946,6 +1956,11 @@ void domark(int signo)
}
SIMPLEQ_FOREACH(f, &fhead, f_link) {
if (f->f_type == F_FORW_UNKN) {
forw_lookup(f);
continue;
}
if (f->f_prevcount && now >= REPEATTIME(f)) {
logit("flush %s: repeated %d times, %d sec.\n",
TypeNames[f->f_type], f->f_prevcount,
@ -2290,14 +2305,13 @@ static void cfopts(char *ptr, struct filed *f)
*/
static struct filed *cfline(char *line)
{
struct addrinfo *ai;
struct filed *f;
char buf[MAXLINE];
char *p, *q, *bp;
int ignorepri = 0;
int singlpri = 0;
int syncfile, pri;
int err, i, i2;
int i, i2;
logit("cfline(%s)\n", line);
@ -2450,21 +2464,7 @@ static struct filed *cfline(char *line)
strlcpy(f->f_un.f_forw.f_hname, p, sizeof(f->f_un.f_forw.f_hname));
strlcpy(f->f_un.f_forw.f_serv, bp, sizeof(f->f_un.f_forw.f_serv));
logit("forwarding host: '%s:%s'\n", p, bp);
err = nslookup(p, bp, &ai);
if (err) {
/*
* The host might be unknown due to an inaccessible
* nameserver (perhaps on the same host). We try to
* get the ip number later, like FORW_SUSP.
*/
f->f_type = F_FORW_UNKN;
f->f_time = time(NULL);
WARN("Cannot find %s, will try again later: %s", p, gai_strerror(err));
} else {
f->f_type = F_FORW;
f->f_un.f_forw.f_addr = ai;
}
forw_lookup(f);
break;
case '|':