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Date: Thu, 16 Apr 2009 11:24:29 -0400
From: Vlad Yasevich <vladislav.yasevich@...com>
To: Christoph Lameter <cl@...ux.com>
CC: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
nhorman@...driver.com, dlstevens@...ibm.com
Subject: Re: PATCH: Multicast: Filter multicast traffic per socket mc_list
Christoph Lameter wrote:
> Do what David Stevens suggest: Add a per socket option
>
>
>
> Subject: Multicast: Filter Multicast traffic per socket mc_list
>
> If two processes open the same port as a multicast socket and then
> join two different multicast groups then traffic for both multicast groups
> is forwarded to either process. This means that application will get surprising
> data that they did not ask for. Applications will have to filter these out in
> order to work correctly if multiple apps run on the same system.
>
> These are pretty strange semantics but they have been around since the
> beginning of multicast support on Unix systems. Most of the other operating
> systems supporting Multicast have since changed to only supplying multicast
> traffic to a socket that was selected through multicast join operations.
>
> This patch does change Linux to behave in the same way. But there may be
> applications that rely on the old behavior. Therefore we provide a means
> to switch back to the old behavior using a new multicast socket option
>
> IP_MULTICAST_ALL
>
> If set then all multicast traffic to the port is forwarded to the socket
> (additional constraints are the SSM inclusion and exclusion lists!).
> If not set (default) then only traffic for multicast groups that were
> joined by thesocket is received.
>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
>
> ---
> include/linux/in.h | 1 +
> include/net/inet_sock.h | 3 ++-
> net/ipv4/igmp.c | 4 ++--
> net/ipv4/ip_sockglue.c | 11 +++++++++++
> 4 files changed, 16 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/include/net/inet_sock.h
> ===================================================================
> --- linux-2.6.orig/include/net/inet_sock.h 2009-04-16 08:59:20.000000000 -0500
> +++ linux-2.6/include/net/inet_sock.h 2009-04-16 09:04:47.000000000 -0500
> @@ -130,7 +130,8 @@ struct inet_sock {
> freebind:1,
> hdrincl:1,
> mc_loop:1,
> - transparent:1;
> + transparent:1,
> + mc_all:1;
> int mc_index;
> __be32 mc_addr;
> struct ip_mc_socklist *mc_list;
> Index: linux-2.6/net/ipv4/igmp.c
> ===================================================================
> --- linux-2.6.orig/net/ipv4/igmp.c 2009-04-16 08:54:47.000000000 -0500
> +++ linux-2.6/net/ipv4/igmp.c 2009-04-16 09:04:06.000000000 -0500
> @@ -2187,7 +2187,7 @@ int ip_mc_sf_allow(struct sock *sk, __be
> struct ip_sf_socklist *psl;
> int i;
>
> - if (!ipv4_is_multicast(loc_addr))
> + if (ipv4_is_lbcast(loc_addr) || !ipv4_is_multicast(loc_addr))
> return 1;
I don't think this change is needed. ipv4_is_lbcast() checks if the
address is 255.255.255.255. That address is already !ipv4_is_multicast().
Subnet broadcasts are also !ipv4_is_multicast.
>
> for (pmc=inet->mc_list; pmc; pmc=pmc->next) {
> @@ -2196,7 +2196,7 @@ int ip_mc_sf_allow(struct sock *sk, __be
> break;
> }
> if (!pmc)
> - return 1;
> + return inet->mc_all;
> psl = pmc->sflist;
> if (!psl)
> return pmc->sfmode == MCAST_EXCLUDE;
> Index: linux-2.6/include/linux/in.h
> ===================================================================
> --- linux-2.6.orig/include/linux/in.h 2009-04-16 09:05:41.000000000 -0500
> +++ linux-2.6/include/linux/in.h 2009-04-16 09:32:52.000000000 -0500
> @@ -107,6 +107,7 @@ struct in_addr {
> #define MCAST_JOIN_SOURCE_GROUP 46
> #define MCAST_LEAVE_SOURCE_GROUP 47
> #define MCAST_MSFILTER 48
> +#define IP_MULTICAST_ALL 49
>
> #define MCAST_EXCLUDE 0
> #define MCAST_INCLUDE 1
> Index: linux-2.6/net/ipv4/ip_sockglue.c
> ===================================================================
> --- linux-2.6.orig/net/ipv4/ip_sockglue.c 2009-04-16 09:09:52.000000000 -0500
> +++ linux-2.6/net/ipv4/ip_sockglue.c 2009-04-16 09:31:40.000000000 -0500
> @@ -449,6 +449,7 @@ static int do_ip_setsockopt(struct sock
> (1<<IP_ROUTER_ALERT) | (1<<IP_FREEBIND) |
> (1<<IP_PASSSEC) | (1<<IP_TRANSPARENT))) ||
> optname == IP_MULTICAST_TTL ||
> + optname == IP_MULTICAST_ALL ||
> optname == IP_MULTICAST_LOOP ||
> optname == IP_RECVORIGDSTADDR) {
> if (optlen >= sizeof(int)) {
> @@ -895,6 +896,13 @@ static int do_ip_setsockopt(struct sock
> kfree(gsf);
> break;
> }
> + case IP_MULTICAST_ALL:
> + if (optlen<1)
> + goto e_inval;
> + if (val != 0 && val != 1)
> + goto e_inval;
> + inet->mc_all = val;
> + break;
> case IP_ROUTER_ALERT:
> err = ip_ra_control(sk, val ? 1 : 0, NULL);
> break;
> @@ -1147,6 +1155,9 @@ static int do_ip_getsockopt(struct sock
> release_sock(sk);
> return err;
> }
> + case IP_MULTICAST_ALL:
> + val = inet->mc_all;
> + break;
> case IP_PKTOPTIONS:
> {
> struct msghdr msg;
You might need to set inet->mc_all to 1 in inet_create() since I am not sure if
we want to change the default behavior. The knowledge that some apps have
a very "unique" way of doing multicast makes me a little hesitant.
-vlad
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