[master] 2387054 Latch error values returned from any VDP function, making sure that all subsequent calls to VDP_bytes() becomes noops. This allows calling code to allow calling VDP_bytes() again even if a previous call returned error.

[Poul-Henning Kamp]

commit 238705413c44c21c5ec91e890e34e1b0c1331066
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Wed Apr 29 09:42:50 2015 +0000

    Latch error values returned from any VDP function, making sure that
    all subsequent calls to VDP_bytes() becomes noops. This allows calling
    code to allow calling VDP_bytes() again even if a previous call
    returned error.
    
    Submitted by: Martin
    
    Fixes #1642
    
    PS: I have given up writing a test-case /phk

diff --git a/bin/varnishd/cache/cache.h b/bin/varnishd/cache/cache.h
index e2207c0..b9c1dd7 100644
--- a/bin/varnishd/cache/cache.h
+++ b/bin/varnishd/cache/cache.h
@@ -616,6 +616,7 @@ struct req {
 	/* Deliver pipeline */
 	struct vdp_entry_s	vdp;
 	struct vdp_entry	*vdp_nxt;
+	unsigned		vdp_errval;
 
 	/* Transaction VSL buffer */
 	struct vsl_log		vsl[1];
diff --git a/bin/varnishd/cache/cache_deliver_proc.c b/bin/varnishd/cache/cache_deliver_proc.c
index a3701a9..a74b41f 100644
--- a/bin/varnishd/cache/cache_deliver_proc.c
+++ b/bin/varnishd/cache/cache_deliver_proc.c
@@ -40,6 +40,8 @@ VDP_bytes(struct req *req, enum vdp_action act, const void *ptr, ssize_t len)
 
 	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
 	assert(act == VDP_NULL || act == VDP_FLUSH);
+	if (req->vdp_errval)
+		return (req->vdp_errval);
 	vdp = req->vdp_nxt;
 	CHECK_OBJ_NOTNULL(vdp, VDP_ENTRY_MAGIC);
 	req->vdp_nxt = VTAILQ_NEXT(vdp, list);
@@ -47,6 +49,8 @@ VDP_bytes(struct req *req, enum vdp_action act, const void *ptr, ssize_t len)
 	assert(act > VDP_NULL || len > 0);
 	/* Call the present layer, while pointing to the next layer down */
 	retval = vdp->func(req, act, &vdp->priv, ptr, len);
+	if (retval)
+		req->vdp_errval = retval; /* Latch error value */
 	req->vdp_nxt = vdp;
 	return (retval);
 }