Re: [libnftnl PATCH 9/9] udata: Store u32 udata values in Big Endian

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Thu, Oct 23, 2025 at 06:05:47PM +0200, Phil Sutter wrote:
> Avoid deviation of this data in between different byte orders. Assume
> that direct callers of nftnl_udata_put() know what they do.

How does this work after an update?

Load ruleset with nft version previous to this, then upgrade, then
list ruleset with new nft version.

> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
>  src/udata.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/src/udata.c b/src/udata.c
> index a1956571ef5fd..8cf4e7ca61e2f 100644
> --- a/src/udata.c
> +++ b/src/udata.c
> @@ -8,6 +8,7 @@
>  #include <udata.h>
>  #include <utils.h>
>  
> +#include <arpa/inet.h>
>  #include <stdlib.h>
>  #include <stdint.h>
>  #include <string.h>
> @@ -100,7 +101,9 @@ EXPORT_SYMBOL(nftnl_udata_put_u32);
>  bool nftnl_udata_put_u32(struct nftnl_udata_buf *buf, uint8_t type,
>  			 uint32_t data)
>  {
> -	return nftnl_udata_put(buf, type, sizeof(data), &data);
> +	uint32_t data_be = htonl(data);
> +
> +	return nftnl_udata_put(buf, type, sizeof(data_be), &data_be);
>  }
>  
>  EXPORT_SYMBOL(nftnl_udata_type);
> @@ -128,7 +131,7 @@ uint32_t nftnl_udata_get_u32(const struct nftnl_udata *attr)
>  
>  	memcpy(&data, attr->value, sizeof(data));
>  
> -	return data;
> +	return ntohl(data);
>  }
>  
>  EXPORT_SYMBOL(nftnl_udata_next);
> -- 
> 2.51.0
>