[PATCH] tcp: Fix build against musl, __sum16 comes from linux/types.h

[PATCH] tcp: Fix build against musl, __sum16 comes from linux/types.h

[Stefano Brivio]

...so we need to include that header explicitly. For some reason, it
works without it when building against glibc.

Reported-by: omni <omni+alpine@hack.org>
Fixes: 3d484aa37090 ("tcp: Update TCP checksum using an iovec array")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 tcp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tcp.c b/tcp.c
index 4e0a17e..429634a 100644
--- a/tcp.c
+++ b/tcp.c
@@ -287,6 +287,8 @@
 #include <time.h>
 #include <arpa/inet.h>
 
+#include <linux/types.h>	/* For __sum16 */
+
 #include "checksum.h"
 #include "util.h"
 #include "iov.h"
-- 
@@ -287,6 +287,8 @@
 #include <time.h>
 #include <arpa/inet.h>
 
+#include <linux/types.h>	/* For __sum16 */
+
 #include "checksum.h"
 #include "util.h"
 #include "iov.h"
-- 
2.43.0

Re: [PATCH] tcp: Fix build against musl, __sum16 comes from linux/types.h

[David Gibson]

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On Wed, Oct 30, 2024 at 09:50:10PM +0100, Stefano Brivio wrote:
> ...so we need to include that header explicitly. For some reason, it
> works without it when building against glibc.

Presumably because glibc indirectly imports linux/types.h at some
point.

But, I think there's a better way to fix this.  We use __sum16 because
it's the type of the checksum field in the linux/tcp.h version of
struct tcphdr.  But we've recently changed to using the netinet/tcp.h
version, which just uses a plain uint16_t.  We should change to match,
and this will go away.

> 
> Reported-by: omni <omni+alpine@hack.org>
> Fixes: 3d484aa37090 ("tcp: Update TCP checksum using an iovec array")
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> ---
>  tcp.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tcp.c b/tcp.c
> index 4e0a17e..429634a 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -287,6 +287,8 @@
>  #include <time.h>
>  #include <arpa/inet.h>
>  
> +#include <linux/types.h>	/* For __sum16 */
> +
>  #include "checksum.h"
>  #include "util.h"
>  #include "iov.h"

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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Re: [PATCH] tcp: Fix build against musl, __sum16 comes from linux/types.h

[Stefano Brivio]

On Thu, 31 Oct 2024 11:34:38 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Wed, Oct 30, 2024 at 09:50:10PM +0100, Stefano Brivio wrote:
> > ...so we need to include that header explicitly. For some reason, it
> > works without it when building against glibc.  
> 
> Presumably because glibc indirectly imports linux/types.h at some
> point.
> 
> But, I think there's a better way to fix this.  We use __sum16 because
> it's the type of the checksum field in the linux/tcp.h version of
> struct tcphdr.  But we've recently changed to using the netinet/tcp.h
> version, which just uses a plain uint16_t.  We should change to match,
> and this will go away.

True, but I thought we would want to keep the 'bitwise' attribute that
comes with __sum16. On the other hand, I see it's only used by
sparse(1), not by gcc itself:

  https://gcc.gnu.org/legacy-ml/gcc-help/2008-03/msg00267.html

so it's rather pointless outside the kernel and we can drop it as well.

I'll change checksum pointers to uint16_t *.

-- 
Stefano