Re: [Qemu-devel] [PATCH v6 4/6] linux-user: Add support for setsockopt() options IPV6_<ADD|DROP>_MEMBERSHIP

[Laurent Vivier <laurent@vivier.eu>]

On 19/05/2019 18:15, Aleksandar Markovic wrote:
> From: Neng Chen <nchen@wavecomp.com>
> 
> Add support for options IPV6_ADD_MEMBERSHIP and IPV6_DROP_MEMPEMBERSHIP
> of the syscall setsockopt(). These options control membership in
> multicast groups. Their argument is a pointer to a struct ipv6_mreq,
> which is in turn defined in IP v6 header netinet/in.h as:
> 
>   struct ipv6_mreq {
>       /* IPv6 multicast address of group */
>       struct  in6_addr  ipv6mr_multiaddr;
>       /* local IPv6 address of interface */
>       int     ipv6mr_interface;
>   };
> 
> ...whereas its definition in kernel's include/uapi/linux/in6.h is:
> 
>   #if __UAPI_DEF_IPV6_MREQ
>   struct ipv6_mreq {
>       /* IPv6 multicast address of group */
>           struct  in6_addr ipv6mr_multiaddr;
>       /* local IPv6 address of interface */
>       int     ipv6mr_ifindex;
>   };
>   #endif
> 
> The first field of ipv6_mreq has the same name ("ipv6mr_multiaddr")
> and type ("in6_addr") in both cases. Moreover, the in6_addr structure
> consists of fields that are always big-endian (on host of any endian),
> therefore the ipv6_mreq's field ipv6mr_multiaddr doesn't need any
> endian conversion.
> 
> The second field of ipv6_mreq may, however, depending on the build
> environment, have different names. This is the reason why the line
> "#if __UAPI_DEF_IPV6_MREQ" is used in this patch - to establish the
> right choice for the field name. Also, endian conversion is needed
> for this field, since it is of type "int".
> 
> Signed-off-by: Neng Chen <nchen@wavecomp.com>
> Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
> ---
>   linux-user/syscall.c | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 96cd4bf..acff14d 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -1892,6 +1892,29 @@ static abi_long do_setsockopt(int sockfd, int level, int optname,
>                                          &pki, sizeof(pki)));
>               break;
>           }
> +        case IPV6_ADD_MEMBERSHIP:
> +        case IPV6_DROP_MEMBERSHIP:
> +        {
> +            struct ipv6_mreq ipv6mreq;
> +
> +            if (optlen < sizeof(ipv6mreq)) {
> +                return -TARGET_EINVAL;
> +            }
> +
> +            if (copy_from_user(&ipv6mreq, optval_addr, sizeof(ipv6mreq))) {
> +                return -TARGET_EFAULT;
> +            }
> +
> +#if __UAPI_DEF_IPV6_MREQ
> +            ipv6mreq.ipv6mr_ifindex = tswap32(ipv6mreq.ipv6mr_ifindex);
> +#else
> +            ipv6mreq.ipv6mr_interface = tswap32(ipv6mreq.ipv6mr_interface);
> +#endif /* __UAPI_DEF_IVP6_MREQ */
> +
> +            ret = get_errno(setsockopt(sockfd, level, optname,
> +                                       &ipv6mreq, sizeof(ipv6mreq)));
> +            break;
> +        }
>           default:
>               goto unimplemented;
>           }
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>