tcp: MAX_WINDOW should be unsigned

Currently MAX_WINDOW is defined as a (signed) int, since '1' is a signed
literal.  This means that when it's used in the SEQ_*() macros, we're
making a signed / unsigned comparison.  While I don't think it was
incorrect in practice, confirming that requires reasoning though arcane
C type promotion rules.

Since it's obviously a non-negative value, change the constant to unsigned.
Change BUF_DISCARD_SIZE for the same reason, and because they're linked
via DISCARD_IOV_NUM, which must also be non-negative.  Change the types
of a few variables in tcp_prepare_iov() to match (otherwise we'd get some
compiler warnings).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

2 files changed, 3 insertions, 4 deletions

diff --git a/tcp.c b/tcp.c
index edcabe2..10d9d0d 100644
--- a/tcp.c
+++ b/tcp.c
@@ -4069,9 +4069,8 @@ int tcp_prepare_iov(struct msghdr *msg, struct iovec *iov,
 		msg->msg_iov = iov + DISCARD_IOV_NUM;
 		msg->msg_iovlen = payload_iov_cnt;
 	} else {
-		int discard_cnt, discard_iov_rem;
+		unsigned discard_cnt, discard_iov_rem, i;
 		struct iovec *iov_start;
-		int i;
 
 		discard_cnt = DIV_ROUND_UP(already_sent, BUF_DISCARD_SIZE);
 		if (discard_cnt > DISCARD_IOV_NUM) {
diff --git a/tcp_internal.h b/tcp_internal.h
index 40472c9..c623569 100644
--- a/tcp_internal.h
+++ b/tcp_internal.h
@@ -12,9 +12,9 @@
 #include "util.h"
 
 #define MAX_WS				8
-#define MAX_WINDOW			(1 << (16 + (MAX_WS)))
+#define MAX_WINDOW			(1U << (16 + (MAX_WS)))
 
-#define BUF_DISCARD_SIZE	(1 << 20)
+#define BUF_DISCARD_SIZE	(1U << 20)
 #define DISCARD_IOV_NUM		DIV_ROUND_UP(MAX_WINDOW, BUF_DISCARD_SIZE)
 
 #define MSS4				ROUND_DOWN(IP_MAX_MTU -		   \