Bug #74334 [Com]: multicurl infinite loop

Edit report at https://bugs.php.net/bug.php?id=74334&edit=1 ID: 74334 Comment by: sean dot bailey at gmail dot com Reported by: julien at palard dot fr Summary: multicurl infinite loop Status: Open Type: Bug Package: cURL related Operating System: Debian GNU/Linux 8.7 (jessie) PHP Version: Irrelevant Block user comment: N Private report: N New Comment: I can confirm this is happening on Fedora 27 as well. Previous Comments: ------------------------------------------------------------------------ [2017-03-29 15:07:22] julien at palard dot fr Follow-up: I tried replacing domain names by IP addresses and it works, so it may be related to name resolution. ------------------------------------------------------------------------ [2017-03-29 15:02:25] julien at palard dot fr Description: ------------ Copying and pasting the example on http://php.net/manual/en/function.curl-multi-init.php give an infinite loop on: while ($active && $mrc == CURLM_OK) { if (curl_multi_select($mh) != -1) { because curl_multi_select always returns -1. I tried stracing but found nothing relevant, there's no syscall during the infinite loop, just before the loop I'm getting: [pid 11348] 1490799411.296356 close(8) = 0 [pid 11348] 1490799411.296397 madvise(0x7f425f426000, 8368128, MADV_DONTNEED) = 0 [pid 11348] 1490799411.296428 exit(0) = ? [pid 11348] 1490799411.296473 +++ exited with 0 +++ [pid 11347] 1490799411.359286 <... poll resumed> ) = 1 ([{fd=9, revents=POLLIN}]) [pid 11347] 1490799411.359362 ioctl(9, FIONREAD, [501]) = 0 [pid 11347] 1490799411.359438 recvfrom(9, "\22>\201\200\0\1\0\2\0\r\0\f\3lxr\3php\3net\0\0\1\0\1\300\f\0"..., 2048, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("167.[redacted].1")}, [28->16]) = 501 [pid 11347] 1490799411.359594 poll([{fd=9, events=POLLIN}], 1, 4915) = 1 ([{fd=9, revents=POLLIN}]) [pid 11347] 1490799411.469988 ioctl(9, FIONREAD, [105]) = 0 [pid 11347] 1490799411.470060 recvfrom(9, "|b\201\200\0\1\0\1\0\1\0\0\3lxr\3php\3net\0\0\34\0\1\300\f\0"..., 65536, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("167.[redacted].1")}, [28->16]) = 105 [pid 11347] 1490799411.470150 close(9) = 0 [pid 11347] 1490799411.470231 madvise(0x7f425fc27000, 8368128, MADV_DONTNEED) = 0 [pid 11347] 1490799411.470284 exit(0) = ? [pid 11347] 1490799411.470346 +++ exited with 0 +++ The presence of [pid …] means that they are forks, not the main process, which is looping. Tested on 7.0.16-3 and 5.6.30-0+deb8u1 (from Debian packages). Test script: --------------- The example on http://php.net/manual/en/function.curl-multi-init.php which is: <?php // create both cURL resources $ch1 = curl_init(); $ch2 = curl_init(); // set URL and other appropriate options curl_setopt($ch1, CURLOPT_URL, "http://lxr.php.net/"); curl_setopt($ch1, CURLOPT_HEADER, 0); curl_setopt($ch2, CURLOPT_URL, "http://www.php.net/"); curl_setopt($ch2, CURLOPT_HEADER, 0); //create the multiple cURL handle $mh = curl_multi_init(); //add the two handles curl_multi_add_handle($mh,$ch1); curl_multi_add_handle($mh,$ch2); $active = null; //execute the handles do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM); while ($active && $mrc == CURLM_OK) { if (curl_multi_select($mh) != -1) { do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM); } } //close the handles curl_multi_remove_handle($mh, $ch1); curl_multi_remove_handle($mh, $ch2); curl_multi_close($mh); ?> Expected result: ---------------- An error or a result. Actual result: -------------- An infinite loop. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=74334&edit=1