[PATCH] uapi/if_arp.h: guard struct definition to not redefine libc's definitions

[PATCH] uapi/if_arp.h: guard struct definition to not redefine libc's definitions

[jane400]

musl libc defines the structs arpreq, arpreq_old and arphdr in
their <net/if_arp.h> header. Guard against a redefinition via
__UAPI_DEF_IF_ARP_ARPREQ for arpreq + arpreq_old and
__UAPI_DEF_IF_ARP_ARPHDR for arphdr.

A follow-up patch for musl is needed for this after this gets picked.

Redefinitions of all the various flags is fine, as this will only
produce warnings with a lenient compiler.

Signed-off-by: Jane Rachinger <jane400@postmarketos.org>
---
 include/uapi/linux/if_arp.h      | 8 ++++++++
 include/uapi/linux/libc-compat.h | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/uapi/linux/if_arp.h b/include/uapi/linux/if_arp.h
index 4783af9fe520..9f2dcc16c013 100644
--- a/include/uapi/linux/if_arp.h
+++ b/include/uapi/linux/if_arp.h
@@ -24,6 +24,7 @@
 #ifndef _UAPI_LINUX_IF_ARP_H
 #define _UAPI_LINUX_IF_ARP_H
 
+#include <linux/libc-compat.h>
 #include <linux/netdevice.h>
 
 /* ARP protocol HARDWARE identifiers. */
@@ -113,6 +114,8 @@
 #define	ARPOP_NAK	10		/* (ATM)ARP NAK			*/
 
 
+#if __UAPI_DEF_IF_ARP_ARPREQ
+
 /* ARP ioctl request. */
 struct arpreq {
 	struct sockaddr	arp_pa;		/* protocol address		 */
@@ -129,6 +132,8 @@ struct arpreq_old {
 	struct sockaddr	arp_netmask;    /* netmask (only for proxy arps) */
 };
 
+#endif
+
 /* ARP Flag values. */
 #define ATF_COM		0x02		/* completed entry (ha valid)	*/
 #define	ATF_PERM	0x04		/* permanent entry		*/
@@ -142,6 +147,8 @@ struct arpreq_old {
  *	This structure defines an ethernet arp header.
  */
 
+#if __UAPI_DEF_IF_ARP_ARPHDR
+
 struct arphdr {
 	__be16		ar_hrd;		/* format of hardware address	*/
 	__be16		ar_pro;		/* format of protocol address	*/
@@ -161,5 +168,6 @@ struct arphdr {
 
 };
 
+#endif
 
 #endif /* _UAPI_LINUX_IF_ARP_H */
diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
index 8254c937c9f4..e722c213f18b 100644
--- a/include/uapi/linux/libc-compat.h
+++ b/include/uapi/linux/libc-compat.h
@@ -194,6 +194,14 @@
 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
 #endif
 
+/* Definitions for if_arp.h */
+#ifndef __UAPI_DEF_IF_ARP_ARPREQ
+#define __UAPI_DEF_IF_ARP_ARPREQ	1
+#endif
+#ifndef __UAPI_DEF_IF_ARP_ARPHDR
+#define __UAPI_DEF_IF_ARP_ARPHDR	1
+#endif
+
 /* Definitions for in.h */
 #ifndef __UAPI_DEF_IN_ADDR
 #define __UAPI_DEF_IN_ADDR		1

base-commit: 89f5e14d05b4852db5ecdf222dc6a13edc633658
-- 
2.46.0

Re: [PATCH] uapi/if_arp.h: guard struct definition to not redefine libc's definitions

[Jakub Kicinski]

On Mon,  9 Sep 2024 11:28:55 +0200 jane400 wrote:

Could you please update the From fields in the email / the author of
the patch to have your full name like the sign off? Right now it says:

 From: jane400 <jane400@postmarketos.org>

> musl libc defines the structs arpreq, arpreq_old and arphdr in

Could you add some reference to when the structs were added to musl?
Web link, or a version number, perhaps?

> diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
> index 8254c937c9f4..e722c213f18b 100644
> --- a/include/uapi/linux/libc-compat.h
> +++ b/include/uapi/linux/libc-compat.h
> @@ -194,6 +194,14 @@
>  #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
>  #endif
>  
> +/* Definitions for if_arp.h */
> +#ifndef __UAPI_DEF_IF_ARP_ARPREQ
> +#define __UAPI_DEF_IF_ARP_ARPREQ	1
> +#endif
> +#ifndef __UAPI_DEF_IF_ARP_ARPHDR
> +#define __UAPI_DEF_IF_ARP_ARPHDR	1
> +#endif
> +
>  /* Definitions for in.h */
>  #ifndef __UAPI_DEF_IN_ADDR
>  #define __UAPI_DEF_IN_ADDR		1
> 
> base-commit: 89f5e14d05b4852db5ecdf222dc6a13edc633658

The code change looks almost good, I think you're missing the code for
handling getting included after the user space, tho? look around how
existing definitions are handled.. 
-- 
pw-bot: cr