netdev - [PATCH 1/2] ipv6: Annotate bitwise IPv6 dsfield pointer cast

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Date:   Fri, 13 Dec 2019 21:24:27 +0100
From:   Sven Eckelmann <sven@...fation.org>
To:     netdev@...r.kernel.org
Cc:     Sven Eckelmann <sven@...fation.org>
Subject: [PATCH 1/2] ipv6: Annotate bitwise IPv6 dsfield pointer cast

The sparse commit 6002ded74587 ("add a flag to warn on casts to/from
bitwise pointers") introduced a check for non-direct casts from/to
restricted datatypes (when -Wbitwise-pointer is enabled).

This triggered a warning in ipv6_get_dsfield() because sparse doesn't know
that the buffer already points to some data in the correct bitwise integer
format. This was already fixed in ipv6_change_dsfield() by the __force
attribute and can be fixed here the same way.

Signed-off-by: Sven Eckelmann <sven@...fation.org>
---
 include/net/dsfield.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/dsfield.h b/include/net/dsfield.h
index 1a245ee10c95..a59a57ffc546 100644
--- a/include/net/dsfield.h
+++ b/include/net/dsfield.h
@@ -21,7 +21,7 @@ static inline __u8 ipv4_get_dsfield(const struct iphdr *iph)

 static inline __u8 ipv6_get_dsfield(const struct ipv6hdr *ipv6h)
 {
-	return ntohs(*(const __be16 *)ipv6h) >> 4;
+	return ntohs(*(__force const __be16 *)ipv6h) >> 4;
 }

-- 
2.20.1