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localhost resolves to IPv4 then IPv6 in unexpected order #11465

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Chilledheart opened this issue Jul 19, 2023 · 1 comment
Closed

localhost resolves to IPv4 then IPv6 in unexpected order #11465

Chilledheart opened this issue Jul 19, 2023 · 1 comment
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@bagder
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name lookup DNS and related tech

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@Chilledheart
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Chilledheart commented Jul 19, 2023 •
edited

Following the thread in #11458. I can confirm the issue is irrelative to proxy setups.

I did this

I pick one VM from mine at IPv6-enabled public network for example.

(IPv6 addresses come at first)

azureuser@east-asia-two:~$ curl -v -I http://www.google.com:12345
*   Trying 2404:6800:4005:810::2004:12345...
*   Trying 142.250.66.100:12345...

(IPv4 addresses come at first)

azureuser@east-asia-two:~$ curl -v -I http://localhost:12345
*   Trying 127.0.0.1:12345...
* connect to 127.0.0.1 port 12345 failed: Connection refused
*   Trying ::1:12345...
* connect to ::1 port 12345 failed: Connection refused

I expected the following

See

curl/lib/hostip.c

Lines 557 to 588 in f2aac0d

static struct Curl_addrinfo *get_localhost(int port, const char *name)
{
struct Curl_addrinfo *ca;
const size_t ss_size = sizeof(struct sockaddr_in);
const size_t hostlen = strlen(name);
struct sockaddr_in sa;
unsigned int ipv4;
unsigned short port16 = (unsigned short)(port & 0xffff);
/* memset to clear the sa.sin_zero field */
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(port16);
if(Curl_inet_pton(AF_INET, "127.0.0.1", (char *)&ipv4) < 1)
return NULL;
memcpy(&sa.sin_addr, &ipv4, sizeof(ipv4));
ca = calloc(sizeof(struct Curl_addrinfo) + ss_size + hostlen + 1, 1);
if(!ca)
return NULL;
ca->ai_flags = 0;
ca->ai_family = AF_INET;
ca->ai_socktype = SOCK_STREAM;
ca->ai_protocol = IPPROTO_TCP;
ca->ai_addrlen = (curl_socklen_t)ss_size;
ca->ai_addr = (void *)((char *)ca + sizeof(struct Curl_addrinfo));
memcpy(ca->ai_addr, &sa, ss_size);
ca->ai_canonname = (char *)ca->ai_addr + ss_size;
strcpy(ca->ai_canonname, name);
ca->ai_next = get_localhost6(port, name);
return ca;
}

the DNS response for localhost is manually crafted, so it is neither done by getaddrinfo nor affected by /etc/hosts file.

To be clear, for some usage of IPv6 localhost, it could be disabled manually by removing the line inside /etc/hosts

(IPv6 addresses come at first)

azureuser@east-asia-two:~$ curl -v -I http://localhost:12345
*   Trying ::1:12345...
* connect to ::1 port 12345 failed: Connection refused
*   Trying 127.0.0.1:12345...
* connect to 127.0.0.1 port 12345 failed: Connection refused

curl/libcurl version

curl 7.81.0 (x86_64-pc-linux-gnu) libcurl/7.81.0 OpenSSL/3.0.2 zlib/1.2.11 brotli/1.0.9 zstd/1.4.8 libidn2/2.3.2 libpsl/0.21.0 (+libidn2/2.3.2) libssh/0.9.6/openssl/zlib nghttp2/1.43.0 librtmp/2.3 OpenLDAP/2.5.14
Release-Date: 2022-01-05
Protocols: dict file ftp ftps gopher gophers http https imap imaps ldap ldaps mqtt pop3 pop3s rtmp rtsp scp sftp smb smbs smtp smtps telnet tftp
Features: alt-svc AsynchDNS brotli GSS-API HSTS HTTP2 HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM NTLM_WB PSL SPNEGO SSL TLS-SRP UnixSockets zstd

operating system

Ubuntu 22.04

Linux east-asia-two 5.15.0-1041-azure #48-Ubuntu SMP Tue Jun 20 20:34:08 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
@Chilledheart
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I can also confirm without get_localhost call, curl can invoke getaddrinfo correctly for localhost:

(base) ➜  build git:(master) ✗ ./src/curl -v -I http://localhost:12345
* processing: http://localhost:12345
*   Trying [::1]:12345...
* connect to ::1 port 12345 failed: Connection refused
*   Trying 127.0.0.1:12345...
* connect to 127.0.0.1 port 12345 failed: Connection refused

with patch

diff --git a/lib/hostip.c b/lib/hostip.c
index 8b452a8e3..633301b1a 100644
--- a/lib/hostip.c
+++ b/lib/hostip.c
@@ -777,8 +777,8 @@ enum resolve_t Curl_resolv(struct Curl_easy *data,
       if(conn->ip_version == CURL_IPRESOLVE_V6 && !Curl_ipv6works(data))
         return CURLRESOLV_ERROR;

-      if(strcasecompare(hostname, "localhost") ||
-         tailmatch(hostname, ".localhost"))
+      if(strcasecompare(hostname, "localhost.fake") ||
+         tailmatch(hostname, ".localhost.fake"))
         addr = get_localhost(port, hostname);
 #ifndef CURL_DISABLE_DOH
       else if(allowDOH && data->set.doh && !ipnum)

@bagder bagder added the name lookup DNS and related tech label Jul 19, 2023
bagder added a commit that referenced this issue Jul 19, 2023
@bagder
hostip: return IPv6 first for "localhost" resolves
20fcc03 
Fixes #11465
Reported-by: Chilledheart on github
@bagder bagder mentioned this issue Jul 19, 2023
Closed
@bagder bagder changed the title Misbehaviour when using localhost compared to other IPv6-compatible hostname localhost resolves to IPv4 then IPv6 in unexpected order Jul 19, 2023
@bagder bagder self-assigned this Jul 19, 2023
@bagder bagder closed this as completed in ac67d72 Jul 19, 2023
bch pushed a commit to bch/curl that referenced this issue Jul 19, 2023
@bagder @bch
hostip: return IPv6 first for localhost resolves
50e67e4 
Fixes curl#11465
Reported-by: Chilledheart on github
Closes curl#11466
Chilledheart added a commit to Chilledheart/yass that referenced this issue Jul 22, 2023
@Chilledheart
tests: workaround with curl localhost resolving
0352f77 
After curl resolves localhost by itself, IPv4 address came first
until recently. For most modern resolver, IPv6 address comes first.

see more at: curl/curl#11465
and: https://daniel.haxx.se/blog/2021/05/31/curl-localhost-as-a-local-host/
Chilledheart added a commit to Chilledheart/yass that referenced this issue Jul 22, 2023
@Chilledheart
tests: workaround with curl localhost resolving
b458f95 
After curl resolves localhost by itself, IPv4 address came first
until recently. For most modern resolver, IPv6 address comes first.

see more at: curl/curl#11465
and: https://daniel.haxx.se/blog/2021/05/31/curl-localhost-as-a-local-host/
@Chilledheart Chilledheart mentioned this issue Jul 22, 2023
Merged
ptitSeb pushed a commit to wasix-org/curl that referenced this issue Sep 25, 2023
@bagder @ptitSeb
hostip: return IPv6 first for localhost resolves
e788412 
Fixes curl#11465
Reported-by: Chilledheart on github
Closes curl#11466
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hostip: return IPv6 first for localhost resolves curl/curl
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