On Mon, Jun 30, 2008 at 06:46:17PM -0400, Chuck Lever wrote:
> My plan is to use an AF_INET listener on systems that support only IPv4,
> and an AF_INET6 listener on systems that can support IPv6. Incoming
> IPv4 packets will be posted to an AF_INET6 listener with a mapped IPv4
> address.
>
> Max Matveev <makc@xxxxxxx> says:
> Creating a single listener can be dangerous - if net.ipv6.bindv6only
> is enabled then it's possible to create another listener in v4
> namespace on the same port and steal the traffic from the "unifed"
> listener. You need to disable V6ONLY explicitly via a sockopt to stop
> that.
Is the V6ONLY option documented anywhere? A quick grep through the
kernel sources and a couple man pages didn't turn up anything.
--b.
>
> Set appropriate socket option on RPC server listener sockets to prevent
> this.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
>
> net/sunrpc/svcsock.c | 12 ++++++++++++
> 1 files changed, 12 insertions(+), 0 deletions(-)
>
>
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 3e65719..43c21f7 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1114,6 +1114,7 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
> struct svc_sock *svsk;
> struct sock *inet;
> int pmap_register = !(flags & SVC_SOCK_ANONYMOUS);
> + int zero = 0;
>
> dprintk("svc: svc_setup_socket %p\n", sock);
> if (!(svsk = kzalloc(sizeof(*svsk), GFP_KERNEL))) {
> @@ -1146,6 +1147,17 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
> else
> svc_tcp_init(svsk, serv);
>
> + /*
> + * We start one listener per sv_serv. We want AF_INET
> + * requests to be automatically shunted to our AF_INET6
> + * listener using a mapped IPv4 address. Make sure
> + * no-one starts an equivalent IPv4 listener, which
> + * would steal our incoming connections.
> + */
> + if (serv->sv_family == AF_INET6)
> + kernel_setsockopt(sock, SOL_IPV6, IPV6_V6ONLY,
> + (char *)&zero, sizeof(zero));
> +
> dprintk("svc: svc_setup_socket created %p (inet %p)\n",
> svsk, svsk->sk_sk);
>
>
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