[PATCH] tap: Revert recently added checks in tap_handler_passt()

[Stefano Brivio <sbrivio@redhat.com>]

This reverts commit 198f87835dc4 ("tap: Return -EIO from
tap_handler_passt() on inconsistent packet stream") and commit
510dace86ccf ("tap: Keep stream consistent if qemu length descriptor
spans two recv() calls").

I can hit occasional failures in perf/passt_tcp tests where we seem
to be getting excess data at the end of a recv(), and for some reason
I couldn't figure out yet, if we just ignore it, subsequent recv()
calls from qemu return correct data. If we close the connection, qemu
can't talk to us anymore, of course.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 tap.c | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/tap.c b/tap.c
index b7ac996..d26af58 100644
--- a/tap.c
+++ b/tap.c
@@ -747,31 +747,19 @@ redo:
 		return -ECONNRESET;
 	}
 
-	while (n > 0) {
-		ssize_t len;
-
-		/* Force receiving at least a complete length descriptor to
-		 * avoid an inconsistent stream.
-		 */
-		if (n < (ssize_t)sizeof(uint32_t)) {
-			rem = recv(c->fd_tap, p + n,
-				   (ssize_t)sizeof(uint32_t) - n, 0);
-			if ((n += rem) != (ssize_t)sizeof(uint32_t))
-				return -EIO;
-		}
-
-		len = ntohl(*(uint32_t *)p);
+	while (n > (ssize_t)sizeof(uint32_t)) {
+		ssize_t len = ntohl(*(uint32_t *)p);
 
 		p += sizeof(uint32_t);
 		n -= sizeof(uint32_t);
 
 		/* At most one packet might not fit in a single read, and this
-		 * also needs to be blocking.
+		 * needs to be blocking.
 		 */
 		if (len > n) {
 			rem = recv(c->fd_tap, p + n, len - n, 0);
 			if ((n += rem) != len)
-				return -EIO;
+				return 0;
 		}
 
 		/* Complete the partial read above before discarding a malformed
-- 
@@ -747,31 +747,19 @@ redo:
 		return -ECONNRESET;
 	}
 
-	while (n > 0) {
-		ssize_t len;
-
-		/* Force receiving at least a complete length descriptor to
-		 * avoid an inconsistent stream.
-		 */
-		if (n < (ssize_t)sizeof(uint32_t)) {
-			rem = recv(c->fd_tap, p + n,
-				   (ssize_t)sizeof(uint32_t) - n, 0);
-			if ((n += rem) != (ssize_t)sizeof(uint32_t))
-				return -EIO;
-		}
-
-		len = ntohl(*(uint32_t *)p);
+	while (n > (ssize_t)sizeof(uint32_t)) {
+		ssize_t len = ntohl(*(uint32_t *)p);
 
 		p += sizeof(uint32_t);
 		n -= sizeof(uint32_t);
 
 		/* At most one packet might not fit in a single read, and this
-		 * also needs to be blocking.
+		 * needs to be blocking.
 		 */
 		if (len > n) {
 			rem = recv(c->fd_tap, p + n, len - n, 0);
 			if ((n += rem) != len)
-				return -EIO;
+				return 0;
 		}
 
 		/* Complete the partial read above before discarding a malformed
-- 
2.35.1