ldap_set_option() performs blocking name resolution during initalization

[Jan Synacek <jsynacek@redhat.com>]

Is it intentional? If yes, could you please explain why, or point me to
a documentation where I can find the answer?

A backtrace and a snippet of code follow:

#0  0x00007fda39c80a70 in __poll_nocancel () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007fda38d17e0d in send_dg (resplen2=0x0, anssizp2=0x0, ansp2=0x0, 
    anscp=0x7fff2548cb30, gotsomewhere=<synthetic pointer>, 
    v_circuit=<synthetic pointer>, ns=0, terrno=0x7fff2548bab0, anssizp=0x7fff2548bbf0, 
    ansp=0x7fff2548baa8, buflen2=0, buf2=0x0, buflen=36, buf=0x7fff2548bc20 "\tg\001", 
    statp=0x7fda39f533e0 <_res@GLIBC_2.2.5>) at res_send.c:1059
#2  __libc_res_nsend (statp=statp@entry=0x7fda39f533e0 <_res@GLIBC_2.2.5>, 
    buf=buf@entry=0x7fff2548bc20 "\tg\001", buflen=<optimized out>, buf2=buf2@entry=0x0, 
    buflen2=buflen2@entry=0, ans=ans@entry=0x7fff2548c700 "", anssiz=anssiz@entry=1024, 
    ansp=ansp@entry=0x7fff2548cb30, ansp2=ansp2@entry=0x0, nansp2=nansp2@entry=0x0, 
    resplen2=resplen2@entry=0x0) at res_send.c:556
#3  0x00007fda38d15d47 in __GI___libc_res_nquery (
    statp=statp@entry=0x7fda39f533e0 <_res@GLIBC_2.2.5>, 
    name=0x7fff2548d140 "client.example.com", class=class@entry=1, type=type@entry=1, 
    answer=answer@entry=0x7fff2548c700 "", anslen=anslen@entry=1024, 
    answerp=answerp@entry=0x7fff2548cb30, answerp2=answerp2@entry=0x0, 
    nanswerp2=nanswerp2@entry=0x0, resplen2=resplen2@entry=0x0) at res_query.c:226
#4  0x00007fda38d16963 in __libc_res_nquerydomain (domain=0x0, resplen2=0x0, 
    nanswerp2=0x0, answerp2=0x0, answerp=0x7fff2548cb30, anslen=1024, 
    answer=0x7fff2548c700 "", type=1, class=1, name=0x7fff2548d140 "client.example.com", 
    statp=0x7fda39f533e0 <_res@GLIBC_2.2.5>) at res_query.c:582
#5  __GI___libc_res_nsearch (statp=0x7fda39f533e0 <_res@GLIBC_2.2.5>, 
    name=name@entry=0x7fff2548d140 "client.example.com", class=class@entry=1, 
    type=type@entry=1, answer=answer@entry=0x7fff2548c700 "", anslen=anslen@entry=1024, 
    answerp=0x7fff2548cb30, answerp2=answerp2@entry=0x0, nanswerp2=nanswerp2@entry=0x0, 
    resplen2=resplen2@entry=0x0) at res_query.c:378
#6  0x00007fda2f2777e4 in __GI__nss_dns_gethostbyname3_r (
    name=name@entry=0x7fff2548d140 "client.example.com", af=af@entry=2, 
    result=result@entry=0x7fff2548d120, buffer=buffer@entry=0x1f33590 "\177", 
    buflen=buflen@entry=992, errnop=errnop@entry=0x7fda3d8966a0, 
    h_errnop=h_errnop@entry=0x7fff2548d10c, ttlp=ttlp@entry=0x0, canonp=canonp@entry=0x0)
    at nss_dns/dns-host.c:192
#7  0x00007fda2f277af0 in _nss_dns_gethostbyname_r (
    name=0x7fff2548d140 "client.example.com", result=0x7fff2548d120, 
    buffer=0x1f33590 "\177", buflen=992, errnop=0x7fda3d8966a0, h_errnop=0x7fff2548d10c)
    at nss_dns/dns-host.c:273
#8  0x00007fda39c9e163 in __gethostbyname_r (
    name=name@entry=0x7fff2548d140 "client.example.com", 
    resbuf=resbuf@entry=0x7fff2548d120, buffer=0x1f33590 "\177", buflen=buflen@entry=992, 
    result=result@entry=0x7fff2548d118, h_errnop=h_errnop@entry=0x7fff2548d10c)
    at ../nss/getXXbyYY_r.c:266
#9  0x00007fda3bb1b3de in ldap_pvt_gethostbyname_a (
    name=name@entry=0x7fff2548d140 "client.example.com", 
    resbuf=resbuf@entry=0x7fff2548d120, buf=buf@entry=0x7fff2548d110, 
    result=result@entry=0x7fff2548d118, herrno_ptr=herrno_ptr@entry=0x7fff2548d10c)
    at util-int.c:350
#10 0x00007fda3bb1b5d0 in ldap_pvt_get_fqdn (name=0x7fff2548d140 "client.example.com", 
    name@entry=0x0) at util-int.c:748
#11 0x00007fda3bb19b47 in ldap_int_initialize (
    gopts=gopts@entry=0x7fda3bd40000 <ldap_int_global_options>, dbglvl=dbglvl@entry=0x0)
    at init.c:645
#12 0x00007fda3bb1a627 in ldap_set_option (ld=0x0, option=24582, invalue=0x7fff2548d2b0)
    at options.c:446
#13 0x00007fda30951cf6 in setup_tls_config (basic_opts=0x1f30450)
    at src/providers/ldap/sdap.c:533
#14 0x00007fda308214b3 in ldap_id_init_internal (bectx=0x1f12b40, ops=0x1f12cb0, 
    pvt_data=0x7fff2548d5e8) at src/providers/ldap/ldap_init.c:146
#15 0x00007fda30821ba0 in sssm_ldap_id_init (bectx=0x1f12b40, ops=0x1f12cb0, 
    pvt_data=0x1f12cb8) at src/providers/ldap/ldap_init.c:199
#16 0x000000000041b227 in load_backend_module (ctx=0x1f12b40, bet_type=BET_ID, 
    bet_info=0x1f12ca8, default_mod_name=0x0) at src/providers/data_provider_be.c:2346
#17 0x000000000041ce4c in be_process_init (mem_ctx=0x1f0ba80, 
    be_domain=0x1f093f0 "localipaldap", ev=0x1f0a630, cdb=0x1f0bb90)
    at src/providers/data_provider_be.c:2520
#18 0x000000000041fde6 in main (argc=3, argv=0x7fff2548e008)
    at src/providers/data_provider_be.c:2743

 735         /* LDAP_OPT_X_TLS_REQUIRE_CERT has to be set as a global option,
 736          * because the SSL/TLS context is initialized from this value. */
 737         ret = ldap_set_option(NULL, LDAP_OPT_X_TLS_REQUIRE_CERT,
 738                               &ldap_opt_x_tls_require_cert);
 739         if (ret != LDAP_OPT_SUCCESS) {
 740             DEBUG(SSSDBG_CRIT_FAILURE,
 741                   "ldap_set_option failed: %s\n",sss_ldap_err2string(ret));
 742             return EIO;
 743         }

Thanks,
-- 
Jan Synacek
Software Engineer, Red Hat