libsa: Fix IP recv timeout

readip() doesn't, at the moment, properly indicate to callers that it has
timed out. One can tell that it's timed out if errno == EAGAIN when it
returns, but this is not ideal. Restructure it a little bit to explicitly
set errno to ETIMEDOUT if we've exhausted tleft.

I found two places that care about where it timed out or not: sendrecv in
net.c and sendrecv_tftp. Both are structured to pass smaller timeout values
to readip while tracking a larger timeout. Neither of them were able to do
this properly with readip not indicating ETIMEDOUT, so fix it.

While here, straighten out the time (t/t1) usage in sendrecv_tftp.

This would have manifested itself in periodic failures to NFS/TFTP boot for
no apparent reason because MINTMO/MAXTMO were not actually being respected
properly. Problems were not reported with NFS, only TFTP.

Reported by:	sbruno
Reviewed by:	sbruno, tsoome
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D14350

3 files changed, 15 insertions, 4 deletions

diff --git a/stand/libsa/ip.c b/stand/libsa/ip.c
index f2293b3cd3f9..ea8213770432 100644
--- a/stand/libsa/ip.c
+++ b/stand/libsa/ip.c
@@ -416,8 +416,13 @@ readip(struct iodesc *d, void **pkt, void **payload, time_t tleft,
 	while ((getsecs() - t) < tleft) {
 		errno = 0;
 		ret = readipv4(d, pkt, payload, tleft, proto);
+		if (ret >= 0)
+			return (ret);
+		/* Bubble up the error if it wasn't successful */
 		if (errno != EAGAIN)
-			break;
+			return (-1);
 	}
-	return (ret);
+	/* We've exhausted tleft; timeout */
+	errno = ETIMEDOUT;
+	return (-1);
 }
diff --git a/stand/libsa/net.c b/stand/libsa/net.c
index ae6e74511e12..5e13c5344327 100644
--- a/stand/libsa/net.c
+++ b/stand/libsa/net.c
@@ -118,7 +118,7 @@ sendrecv(struct iodesc *d,
 		/* Try to get a packet and process it. */
 		cc = (*rproc)(d, pkt, payload, tleft);
 		/* Return on data, EOF or real error. */
-		if (cc != -1 || errno != 0)
+		if (cc != -1 || (errno != 0 && errno != ETIMEDOUT))
 			return (cc);
 
 		/* Timed out or didn't get the packet we're waiting for */
diff --git a/stand/libsa/tftp.c b/stand/libsa/tftp.c
index 9bef4643d25f..da85b9842785 100644
--- a/stand/libsa/tftp.c
+++ b/stand/libsa/tftp.c
@@ -638,14 +638,20 @@ sendrecv_tftp(struct tftp_handle *h,
 		if (cc == -1) {
 			/* Error on transmit; wait before retrying */
 			while ((getsecs() - t1) < tleft);
+			t1 = getsecs();
 			continue;
 		}
 
+		t = t1 = getsecs();
 recvnext:
+		if ((getsecs() - t) > MAXTMO) {
+			errno = ETIMEDOUT;
+			return -1;
+		}
 		/* Try to get a packet and process it. */
 		cc = (*rproc)(h, pkt, payload, tleft, rtype);
 		/* Return on data, EOF or real error. */
-		if (cc != -1 || errno != 0)
+		if (cc != -1 || (errno != 0 && errno != ETIMEDOUT))
 			return (cc);
 		if ((getsecs() - t1) < tleft) {
 		    goto recvnext;