[master] f2a7810 Fix ESI Parsing when VEP_Parse is called on tag which shares a prefix with another

[Nils Goroll]

commit f2a7810d7b12dc2f3406d31daa81f0e4e9b5b469
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Dec 14 15:21:41 2016 +0100

    Fix ESI Parsing when VEP_Parse is called on tag which shares a prefix with another
    
    Example for the case addressed here is an html comment which is not esi.
    
    	1st call on !--e
    	2nd call on !--end
    
    The first call could match !--esi:, so vep_match() does not return with
    VEP_NOTMYTAG, but with null, so characters up until 'e' are marked.
    
    For the second call, we need to consider the case that characters after
    the end of the tag could already be marked.
    
    Fixes #1988

diff --git a/bin/varnishd/cache/cache_esi_parse.c b/bin/varnishd/cache/cache_esi_parse.c
index 45d5f48..7f17cc3 100644
--- a/bin/varnishd/cache/cache_esi_parse.c
+++ b/bin/varnishd/cache/cache_esi_parse.c
@@ -946,8 +946,11 @@ VEP_Parse(struct vep_state *vep, const char *p, size_t l)
 			} else {
 				vep->match_hit = vm;
 				vep->state = *vm->state;
-				if (vm->match != NULL)
-					p += strlen(vm->match) - vep->tag_i;
+				if (vm->match != NULL) {
+					i = strlen(vm->match);
+					if (i > vep->tag_i)
+						p += i - vep->tag_i;
+				}
 				vep->match = NULL;
 				vep->tag_i = 0;
 			}
diff --git a/bin/varnishtest/tests/e00019.vtc b/bin/varnishtest/tests/e00019.vtc
index 1010eab..88aa405 100644
--- a/bin/varnishtest/tests/e00019.vtc
+++ b/bin/varnishtest/tests/e00019.vtc
@@ -21,6 +21,10 @@ server s1 {
 	chunkedlen 65536
 	chunked {<esi:comment/>}
 
+	chunked {<!--e}
+	delay .4
+	chunked {nd:comment>}
+
 	chunkedlen 0
 } -start
 
@@ -55,8 +59,8 @@ client c1 {
 	txreq  -url bar
 	rxresp
 	expect resp.status == 200
-	expect resp.bodylen == 65840
+	expect resp.bodylen == 65856
 } -run
 
-varnish v1 -expect esi_errors == 4
+varnish v1 -expect esi_errors == 5
 varnish v1 -expect esi_warnings == 1