curl_easy_duphandle() bug after 7.69.1

[kn007]

I try it on 7.69.1 and 7.69.2-dev, same problem. 7.69.0 working well.

  OS               Linux CentOS Linux release 8.1.1911 (Core)
  Kernel           5.5.5-1.el8.elrepo.x86_64

--disable-static --enable-threaded-resolver --with-gssapi --with-nghttp2 --enable-ares

curl 7.69.2-DEV (x86_64-pc-linux-gnu) libcurl/7.69.2-DEV OpenSSL/1.1.1c-fips zlib/1.2.11 c-ares/1.16.0 libidn2/2.2.0 nghttp2/1.40.0
Release-Date: [unreleased]
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp
Features: AsynchDNS GSS-API HTTP2 HTTPS-proxy IDN Kerberos Largefile libz NTLM NTLM_WB SPNEGO SSL TLS-SRP UnixSockets

dnf:

CentOS-8 - AppStream                                                                                             0.0  B/s |   0  B     00:00
Error: Failed to download metadata for repo 'AppStream': Cannot prepare internal mirrorlist: curl_easy_duphandle() call failed

git:

Cloning into 'curl'...
warning: curl_multi_add_handle failed: Invalid easy handle
fatal: unable to access 'https://github.com/curl/curl/': failed to start HTTP request

[bagder]

Can you provide a simple stand-alone example code showing this problem? Both the tools you refer to above are huge and complex applications that make things really hard to debug or even understand what they're doing.

[kn007]

Sorry, I'm afraid that I can't.
I guess it happened after commit: c8f086b
let me try it.

[kn007]

My guess is correct.
After run
git reset --hard e364546fb3371ac27f59f897e4c55acce7fc824e
make curl and it working fine.

but reset to c8f086b , it's broken..

Sorry that I could not get more information.

[bagder]

I still can't see what's wrong in there...

[jay]

If c-ares is too old or IPv6 support is disabled (like is the case here) those functions could return CURLE_NOT_BUILT_IN:

curl/lib/asyn-ares.c

Lines 788 to 812 in b81e0b0

	CURLcode Curl_set_dns_local_ip6(struct Curl_easy *data,
	const char *local_ip6)
	{
	#if (ARES_VERSION >= 0x010704) && defined(ENABLE_IPV6)
	unsigned char a6[INET6_ADDRSTRLEN];
	if((!local_ip6) || (local_ip6[0] == 0)) {
	/* disabled: do not bind to a specific address */
	memset(a6, 0, sizeof(a6));
	}
	else {
	if(Curl_inet_pton(AF_INET6, local_ip6, a6) != 1) {
	return CURLE_BAD_FUNCTION_ARGUMENT;
	}
	}
	ares_set_local_ip6((ares_channel)data->state.resolver, a6);
	return CURLE_OK;
	#else /* c-ares version too old! */
	(void)data;
	(void)local_ip6;
	return CURLE_NOT_BUILT_IN;
	#endif
	}

I don't know for sure this is the problem but I don't see what else it could be. #5100 should fix this, @kn007 can you please try it?

[kn007]

Ok, let me try it, wait a minute.

my c-ares is 1.16.0, IPv6 is disabled.

[kn007]

@jay Yes, it's working fine after patch #5100 .
Thanks for your work.

[bagder]

But why is the build IPv6-disabled, no such configure option was shown?

[kn007]

I don't know.
My OS disabled the ipv6 on grub.

GRUB_CMDLINE_LINUX = ... ipv6.disable=1

Some people like me, will change it on the sysctl.conf file.