From 59aa6fdad4f89279f5106a4be0fdc7588117c706 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gustaf=20Alh=C3=A4ll?= <gustaf@hanicef.me>
Date: Thu, 14 Dec 2023 17:00:20 +0100
Subject: [PATCH] Fix ban mask being ignored on IPv6 addresses

---
 src/netcode/i_tcp.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/netcode/i_tcp.c b/src/netcode/i_tcp.c
index c70290e54..d91583e25 100644
--- a/src/netcode/i_tcp.c
+++ b/src/netcode/i_tcp.c
@@ -404,6 +404,20 @@ static const char *SOCK_GetBanMask(size_t ban)
 	return NULL;
 }
 
+#ifdef HAVE_IPV6
+static boolean SOCK_cmpipv6(mysockaddr_t *a, mysockaddr_t *b, UINT8 mask)
+{
+	UINT8 bitmask;
+	I_Assert(mask <= 128);
+	if (memcmp(&a->ip6.sin6_addr, &b->ip6.sin6_addr, mask / 8) != 0)
+		return false;
+	if (mask % 8 == 0)
+		return true;
+	bitmask = 255 << (mask % 8);
+	return (a->ip6.sin6_addr.s6_addr[mask / 8] & bitmask) == (b->ip6.sin6_addr.s6_addr[mask / 8] & bitmask);
+}
+#endif
+
 static boolean SOCK_cmpaddr(mysockaddr_t *a, mysockaddr_t *b, UINT8 mask)
 {
 	UINT32 bitmask = INADDR_NONE;
@@ -416,7 +430,7 @@ static boolean SOCK_cmpaddr(mysockaddr_t *a, mysockaddr_t *b, UINT8 mask)
 			&& (b->ip4.sin_port == 0 || (a->ip4.sin_port == b->ip4.sin_port));
 #ifdef HAVE_IPV6
 	else if (b->any.sa_family == AF_INET6)
-		return !memcmp(&a->ip6.sin6_addr, &b->ip6.sin6_addr, sizeof(b->ip6.sin6_addr))
+		return SOCK_cmpipv6(a, b, mask)
 			&& (b->ip6.sin6_port == 0 || (a->ip6.sin6_port == b->ip6.sin6_port));
 #endif
 	else