Try to make the H1 state engine look more like one.

bin/varnishd/cache/cache_session.c

@@ -330,7 +330,6 @@ SES_Proto_Sess(struct worker *wrk, void *arg)
 	    cache_param->http_req_size, cache_param->http_req_hdr_len);
 
 	if (sp->sess_step < S_STP_H1_LAST) {
-		sp->sess_step = S_STP_H1NEWREQ;
 		wrk->task.func = SES_Proto_Req;
 		wrk->task.priv = req;
 	} else if (sp->sess_step < S_STP_PROXY_LAST) {

bin/varnishd/http1/cache_http1_fsm.c

@@ -331,10 +331,33 @@ HTTP1_Session(struct worker *wrk, struct req *req)
 		return;
 	}
 
+
+	while (1) {
+		switch (sp->sess_step) {
+		case S_STP_H1NEWSESS:
+			if (VTCP_blocking(sp->fd)) {
+				if (errno == ECONNRESET)
+					SES_Close(sp, SC_REM_CLOSE);
+				else
+					SES_Close(sp, SC_TX_ERROR);
+				AN(http1_cleanup(sp, wrk, req));
+				return;
+			}
+			sp->sess_step = S_STP_H1NEWREQ;
+			break;
+		case S_STP_H1NEWREQ:
+			nxt = http1_wait(sp, wrk, req);
+			if (nxt != REQ_FSM_MORE)
+				return;
+			sp->sess_step = S_STP_H1WORKING;
+			req->req_step = R_STP_RECV;
+			break;
+		case S_STP_H1BUSY:
 			/*
-	 * Return from waitinglist. Check to see if the remote has left.
+			 * Return from waitinglist.
+			 * Check to see if the remote has left.
 			 */
-	if (req->req_step == R_STP_LOOKUP && VTCP_check_hup(sp->fd)) {
+			if (VTCP_check_hup(sp->fd)) {
 				AN(req->hash_objhead);
 				(void)HSH_DerefObjHead(wrk, &req->hash_objhead);
 				AZ(req->hash_objhead);
@@ -342,20 +365,21 @@ HTTP1_Session(struct worker *wrk, struct req *req)
 				AN(http1_cleanup(sp, wrk, req));
 				return;
 			}
-
-	while (1) {
+			sp->sess_step = S_STP_H1WORKING;
+			break;
+		case S_STP_H1WORKING:
 			assert(
-		    sp->sess_step == S_STP_H1NEWREQ ||
 			    req->req_step == R_STP_LOOKUP ||
 			    req->req_step == R_STP_RECV);
 
-		if (sp->sess_step == S_STP_H1WORKING) {
 			if (req->req_step == R_STP_RECV)
 				nxt = http1_dissect(wrk, req);
 			if (nxt == REQ_FSM_MORE)
 				nxt = CNT_Request(wrk, req);
-			if (nxt == REQ_FSM_DISEMBARK)
+			if (nxt == REQ_FSM_DISEMBARK) {
+				sp->sess_step = S_STP_H1BUSY;
 				return;
+			}
 			assert(nxt == REQ_FSM_DONE);
 			if (http1_cleanup(sp, wrk, req))
 				return;
@@ -373,14 +397,10 @@ HTTP1_Session(struct worker *wrk, struct req *req)
 					wrk->stats->sess_readahead++;
 				sp->sess_step = S_STP_H1NEWREQ;
 			}
+			break;
+		default:
+			WRONG("Wrong H1 session state");
 		}
 
-		if (sp->sess_step == S_STP_H1NEWREQ) {
-			nxt = http1_wait(sp, wrk, req);
-			if (nxt != REQ_FSM_MORE)
-				return;
-			sp->sess_step = S_STP_H1WORKING;
-			req->req_step = R_STP_RECV;
-		}
 	}
 }