[6.0] 3c946ae41 Adjust the minimum value of h2_initial_window_size

[Dridi Boukelmoune]

commit 3c946ae41555655fc60c3e69bed573fae3775af6
Author: Martin Blix Grydeland <martin at varnish-software.com>
Date:   Tue Apr 27 14:58:58 2021 +0200

    Adjust the minimum value of h2_initial_window_size
    
    We have a strict min at the protocol default here. This is because we
    don't have the 'use settings only after peer ack' in place yet. If the
    value is lower than the protocol default, the very first stream could get
    a flow control error.

diff --git a/include/tbl/params.h b/include/tbl/params.h
index 053666de4..7a9cf2897 100644
--- a/include/tbl/params.h
+++ b/include/tbl/params.h
@@ -1832,10 +1832,14 @@ PARAM(
        /* func */      NULL
 )
 
+/* We have a strict min at the protocol default here. This is because we
+ * don't have the 'use settings only after peer ack' in place yet. If the
+ * value is lower than the protocol default, the very first stream could
+ * get a flow control error. */
 PARAM(
 	/* name */      h2_initial_window_size,
 	/* typ */       bytes_u,
-	/* min */       "0",
+	/* min */       "65535b",
 	/* max */       "2147483647b",
 	/* default */   "65535b",
 	/* units */     "bytes",