2008-07-19 01:06:01

by [email protected]

[permalink] [raw]
Subject: Re: [PATCH 7/8] SUNRPC: Set V6ONLY socket option for RPC listener sockets

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 <[email protected]> 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 <[email protected]>
> ---
>
> 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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2008-07-21 19:32:42

by Chuck Lever III

[permalink] [raw]
Subject: Re: [PATCH 7/8] SUNRPC: Set V6ONLY socket option for RPC listener sockets

On Fri, Jul 18, 2008 at 9:05 PM, J. Bruce Fields <[email protected]> wrote:
> 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 <[email protected]> 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.

I didn't find anything that documented it, so I based this patch on
studying pieces of the IPv6 code that use this flag. It would be
worth passing this patch by netdev.

>>
>> Set appropriate socket option on RPC server listener sockets to prevent
>> this.
>>
>> Signed-off-by: Chuck Lever <[email protected]>
>> ---
>>
>> 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);
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>> the body of a message to [email protected]
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to [email protected]
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>



--
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