commit cf758c3329364c1516e2b78c573d6901843bc670
from: Omar Polo <op@omarpolo.com>
date: Tue Dec 14 22:12:20 2021 UTC

fix Tattach handling

The previous implementation assumed that you can't attach more than
once.  This is clearly wrong, Tattach and Twalk are the two ways to
obtain new fids.

This drops the error on subsequential attach and making the test
"multiple attach" passes.

commit - a47c234bedbcc16108a0e4f03b6f333ef72729c8
commit + cf758c3329364c1516e2b78c573d6901843bc670
blob - 942a9436ab608ca818a0e6788a6d48774c385bbe
blob + 5acf852dec04af7440d6eb40c4a8f159f7f7a8b4
--- client.c
+++ client.c
@@ -76,7 +76,7 @@ static struct imsgev	*iev_listener;
 static struct evbuffer	*evb;
 static uint32_t		 peerid;
 
-static int		 handshaked, attached;
+static int		 handshaked;
 uint32_t		 msize;
 
 static ATTR_DEAD void	client_shutdown(void);
@@ -411,9 +411,6 @@ qid_decref(struct qid *qid)
 
 	close(qid->fd);
 	free(qid);
-
-	if (STAILQ_EMPTY(&qids))
-		attached = 0;
 }
 
 static struct fid *
@@ -781,11 +778,6 @@ tattach(struct np_msg_header *hdr, const uint8_t *data
 	uint32_t	 fid, afid;
 	int		 fd;
 	char		 aname[PATH_MAX];
-
-	if (attached) {
-		np_error(hdr->tag, "already attached");
-		return;
-	}
 
 	/* fid[4] afid[4] uname[s] aname[s] */
 
@@ -807,6 +799,11 @@ tattach(struct np_msg_header *hdr, const uint8_t *data
 		goto err;
 	case READSTRTRUNC:
 		np_error(hdr->tag, "name too long");
+		return;
+	}
+
+	if (fid_by_id(fid) != NULL || afid != NOFID) {
+		np_error(hdr->tag, "invalid fid or afid");
 		return;
 	}
 
@@ -816,7 +813,7 @@ tattach(struct np_msg_header *hdr, const uint8_t *data
 	if ((qid = qid_from_fd(fd, NULL, NULL)) == NULL)
 		goto fail;
 
-	log_debug("attached %s", aname);
+	log_debug("attached %s to %d", aname, fid);
 
 	if ((f = new_fid(qid, fid)) == NULL) {
 		qid_decref(qid);
@@ -824,7 +821,6 @@ tattach(struct np_msg_header *hdr, const uint8_t *data
 	}
 
 	np_attach(hdr->tag, qid);
-	attached = 1;
 	return;
 
 fail: