From ab9befbe4118850bcd58b33064f020d69b44dea6 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 7 Nov 2017 20:14:43 +0900
Subject: netlink: make sure we reserve space for NLMSG_DONE

Otherwise, if messages pack really close together, we'll exceed the size
of the sk_buff and return ENOBUFS. I suspect this has been the cause of
a lot of weird bugs that people just worked around by increasing the
receive buffer size. This actually addresses the root cause.
---
 src/compat/compat.h | 17 ++++++++++++++++-
 src/tests/netns.sh  |  9 +++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/compat/compat.h b/src/compat/compat.h
index 9ec73ba..e4dd226 100644
--- a/src/compat/compat.h
+++ b/src/compat/compat.h
@@ -454,16 +454,31 @@ static inline struct nlattr **genl_family_attrbuf(const struct genl_family *fami
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 14, 0)
 #define get_device_dump(a, b) get_device_dump_real(a, b); \
 static int get_device_dump(a, b) { \
+	int ret; \
 	struct wireguard_device *wg = (struct wireguard_device *)cb->args[0]; \
 	if (!wg) { \
 		int ret = get_device_start(cb); \
 		if (ret) \
 			return ret; \
 	} \
-	return get_device_dump_real(skb, cb); \
+	/* https://patchwork.kernel.org/patch/10046511/ */ \
+	skb->end -= nlmsg_total_size(sizeof(int)); \
+	ret = get_device_dump_real(skb, cb); \
+	skb->end += nlmsg_total_size(sizeof(int)); \
+	return ret; \
 } \
 static int get_device_dump_real(a, b)
 #define COMPAT_CANNOT_USE_NETLINK_START
+#else /* https://patchwork.kernel.org/patch/10046511/ */
+#define get_device_dump(a, b) get_device_dump_real(a, b); \
+static int get_device_dump(a, b) { \
+	int ret; \
+	skb->end -= nlmsg_total_size(sizeof(int)); \
+	ret = get_device_dump_real(skb, cb); \
+	skb->end += nlmsg_total_size(sizeof(int)); \
+	return ret; \
+} \
+static int get_device_dump_real(a, b)
 #endif
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 17, 0)
diff --git a/src/tests/netns.sh b/src/tests/netns.sh
index 9a12a19..2ad8d88 100755
--- a/src/tests/netns.sh
+++ b/src/tests/netns.sh
@@ -415,6 +415,15 @@ while read -r line; do
 done < <(n0 wg show wg0 allowed-ips)
 ((i == 40))
 ip0 link del wg0
+ip0 link add wg0 type wireguard
+config=( )
+for i in {1..29}; do
+	config+=( "[Peer]" "PublicKey=$(wg genkey)" )
+done
+config+=( "[Peer]" "PublicKey=$(wg genkey)" "AllowedIPs=255.2.3.4/32,abcd::255/128" )
+n0 wg setconf wg0 <(printf '%s\n' "${config[@]}")
+n0 wg showconf wg0 > /dev/null
+ip0 link del wg0
 
 ! n0 wg show doesnotexist || false
 
-- 
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