altsvc: accept and parse IPv6 addresses in response headers

Store numerical IPv6 addresses in the alt-svc file with the brackets
present.

Verify with test 437 and 438

Fixes #11737
Reported-by: oliverpool on github
Closes #11743

tests/data/Makefile.inc

@@ -70,7 +70,7 @@ test399 test400 test401 test402 test403 test404 test405 test406 test407 \
 test408 test409 test410 test411 test412 test413 test414 test415 test416 \
 test417 test418 test419 test420 test421 test422 test423 test424 test425 \
 test426 test427 test428 test429 test430 test431 test432 test433 test434 \
-test435 test436 \
+test435 test436 test437 test438 \
 \
 test440 test441 test442 test443 test444 test445 test446 test447 test448 \
 test449 test450 test451 test452 test453 test454 test455 test456 \

tests/data/test437

@@ -0,0 +1,68 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+Alt-Svc
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-head: yesyes
+Alt-Svc: h1="[ffff::1]:8181"
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+debug
+alt-svc
+</features>
+<server>
+http
+</server>
+ <name>
+Alt-Svc to numerical IPv6 address
+ </name>
+<setenv>
+# make debug-curl accept Alt-Svc over plain HTTP
+CURL_ALTSVC_HTTP="yeah"
+</setenv>
+ <command>
+http://%HOSTIP:%HTTPPORT/%TESTNUMBER --alt-svc "%LOGDIR/altsvc-%TESTNUMBER"
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+GET /%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+<stripfile>
+# strip out the (dynamic) expire date from the file so that the rest
+# matches
+s/\"([^\"]*)\"/TIMESTAMP/
+</stripfile>
+<file name="%LOGDIR/altsvc-%TESTNUMBER" mode="text">
+# Your alt-svc cache. https://curl.se/docs/alt-svc.html
+# This file was generated by libcurl! Edit at your own risk.
+h1 %HOSTIP %HTTPPORT h1 [ffff::1] 8181 TIMESTAMP 0 0
+</file>
+</verify>
+</testcase>

tests/data/test438

@@ -0,0 +1,90 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+Alt-Svc
+HTTP/2
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-Head: yesyes
+Alt-Svc: h1="%HOST6IP:%HTTP6PORT", ma=315360000; persist=0
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+alt-svc
+debug
+ipv6
+</features>
+<server>
+http
+http-ipv6
+</server>
+ <name>
+HTTPS IPv4 GET translated by alt-svc to IPv6 address
+ </name>
+<setenv>
+# make debug-curl accept Alt-Svc over plain HTTP
+CURL_ALTSVC_HTTP="yeah"
+</setenv>
+ <command>
+--alt-svc "%LOGDIR/altsvc-%TESTNUMBER" "http://%HOSTIP:%HTTPPORT/%TESTNUMBER" "http://%HOSTIP:%HTTPPORT/%TESTNUMBER"
+</command>
+<file name="%LOGDIR/altsvc-%TESTNUMBER">
+h1 %HOSTIP %HTTPPORT h1 %HOST6IP %HTTP6PORT "20290222 22:19:28" 0 0
+</file>
+
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<stdout>
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-Head: yesyes
+Alt-Svc: h1="%HOST6IP:%HTTP6PORT", ma=315360000; persist=0
+
+-foo-
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-Head: yesyes
+Alt-Svc: h1="%HOST6IP:%HTTP6PORT", ma=315360000; persist=0
+
+-foo-
+</stdout>
+<stripfile>
+s/^server: nghttpx.*\r?\n//
+# strip out the (dynamic) expire date from the file so that the rest
+# matches
+s/\"2([^\"]*)\"/TIMESTAMP/
+</stripfile>
+<file name="%LOGDIR/altsvc-%TESTNUMBER" mode="text">
+# Your alt-svc cache. https://curl.se/docs/alt-svc.html
+# This file was generated by libcurl! Edit at your own risk.
+h1 %HOSTIP %HTTPPORT h1 %HOST6IP %HTTP6PORT TIMESTAMP 0 0
+</file>
+</verify>
+</testcase>