CURLOPT_ALTSVC.3: document the file format

Closes #9033

diff --git a/docs/libcurl/opts/CURLOPT_ALTSVC.3 b/docs/libcurl/opts/CURLOPT_ALTSVC.3
index d9875022d9b3691e911000c975b23349023c95f9..38c2bab2565978f2dec398984749a5bd933dee8d 100644 (file)
--- a/docs/libcurl/opts/CURLOPT_ALTSVC.3
+++ b/docs/libcurl/opts/CURLOPT_ALTSVC.3
@@ -51,6 +51,35 @@ if(curl) {
   curl_easy_perform(curl);
 }
 .fi
+.SH "FILE FORMAT"
+A text based file with one line per alt-svc entry and each line consists of
+nine space-separated fields.
+
+An example line could look like
+
+ h2 www.example 8443 h3 quic.example 443 "20190808 06:18:37" 1 0
+
+The fields of that line are:
+
+.IP h2
+ALPN id for the source origin
+.IP www.example
+Host name for the source origin
+.IP 8443
+Port number for the source origin
+.IP h3
+ALPN id for the destination host
+.IP quic.example
+Host name for the destination host
+.IP 443
+Port number for the destination host
+.IP 2019*
+Expiration date and time of this entry within double quotes. The date format
+is "YYYYMMDD HH:MM:SS" and the time zone is GMT.
+.IP 1
+Boolean (1 or 0) if "persist" was set for this entry
+.IP 0
+Integer priority value (not currently used)
 .SH AVAILABILITY
 Added in 7.64.1
 .SH RETURN VALUE