--- v2.4.5/linux/include/linux/inetdevice.h~ Sun Jul 1 11:05:50 2001 +++ linux/include/linux/inetdevice.h Sun Jul 1 13:08:45 2001 @@ -18,6 +18,7 @@ int mc_forwarding; int tag; int arp_filter; + int forward_shared; void *sysctl; }; @@ -56,6 +57,8 @@ (ipv4_devconf.accept_redirects || (in_dev)->cnf.accept_redirects))) #define IN_DEV_ARPFILTER(in_dev) (ipv4_devconf.arp_filter || (in_dev)->cnf.arp_filter) + +#define IN_DEV_FORWARD_SHARED(in_dev) ((in_dev)->cnf.forward_shared && ipv4_devconf.forward_shared) struct in_ifaddr { --- v2.4.5/linux/include/linux/sysctl.h~ Sun Jul 1 11:05:50 2001 +++ linux/include/linux/sysctl.h Sun Jul 1 14:02:39 2001 @@ -325,7 +325,8 @@ NET_IPV4_CONF_BOOTP_RELAY=10, NET_IPV4_CONF_LOG_MARTIANS=11, NET_IPV4_CONF_TAG=12, - NET_IPV4_CONF_ARPFILTER=13 + NET_IPV4_CONF_ARPFILTER=13, + NET_IPV4_CONF_FORWARD_SHARED=14, }; /* /proc/sys/net/ipv6 */ --- v2.4.5/linux/net/ipv4/devinet.c~ Sun Jul 1 11:05:50 2001 +++ linux/net/ipv4/devinet.c Sun Jul 1 12:30:43 2001 @@ -1016,7 +1016,7 @@ static struct devinet_sysctl_table { struct ctl_table_header *sysctl_header; - ctl_table devinet_vars[14]; + ctl_table devinet_vars[15]; ctl_table devinet_dev[2]; ctl_table devinet_conf_dir[2]; ctl_table devinet_proto_dir[2]; @@ -1061,6 +1061,9 @@ &proc_dointvec}, {NET_IPV4_CONF_ARPFILTER, "arp_filter", &ipv4_devconf.arp_filter, sizeof(int), 0644, NULL, + &proc_dointvec}, + {NET_IPV4_CONF_FORWARD_SHARED, "forward_shared", + &ipv4_devconf.forward_shared, sizeof(int), 0644, NULL, &proc_dointvec}, {0}}, --- v2.4.5/linux/include/net/ip_fib.h~ Sun Jul 1 11:04:32 2001 +++ linux/include/net/ip_fib.h Sun Jul 1 14:11:54 2001 @@ -203,7 +203,7 @@ extern int inet_rtm_getroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg); extern int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb); extern int fib_validate_source(u32 src, u32 dst, u8 tos, int oif, - struct net_device *dev, u32 *spec_dst, u32 *itag); + struct net_device *dev, u32 *spec_dst, u32 *itag, int our); extern void fib_select_multipath(const struct rt_key *key, struct fib_result *res); /* Exported by fib_semantics.c */ --- v2.4.5/linux/net/ipv4/fib_frontend.c~ Sun Jul 1 11:05:50 2001 +++ linux/net/ipv4/fib_frontend.c Sun Jul 1 14:36:45 2001 @@ -204,13 +204,15 @@ */ int fib_validate_source(u32 src, u32 dst, u8 tos, int oif, - struct net_device *dev, u32 *spec_dst, u32 *itag) + struct net_device *dev, u32 *spec_dst, u32 *itag, + int our) { struct in_device *in_dev; struct rt_key key; struct fib_result res; int no_addr, rpf; int ret; + int fwdsh = 0; key.dst = src; key.src = dst; @@ -225,6 +227,7 @@ if (in_dev) { no_addr = in_dev->ifa_list == NULL; rpf = IN_DEV_RPFILTER(in_dev); + fwdsh = IN_DEV_FORWARD_SHARED(in_dev); } read_unlock(&inetdev_lock); @@ -233,7 +236,12 @@ if (fib_lookup(&key, &res)) goto last_resort; - if (res.type != RTN_UNICAST) + if (fwdsh) { + fwdsh = (res.type == RTN_LOCAL && !our); + if (fwdsh) + rpf = 0; + } + if (res.type != RTN_UNICAST && !fwdsh) goto e_inval_res; *spec_dst = FIB_RES_PREFSRC(res); if (itag) @@ -254,6 +262,8 @@ if (rpf) goto e_inval; key.oif = dev->ifindex; + if (fwdsh) + key.iif = loopback_dev.ifindex; ret = 0; if (fib_lookup(&key, &res) == 0) { --- v2.4.5/linux/net/ipv4/route.c~ Sun Jul 1 11:05:50 2001 +++ linux/net/ipv4/route.c Sun Jul 1 11:07:09 2001 @@ -1206,7 +1206,7 @@ goto e_inval; spec_dst = inet_select_addr(dev, 0, RT_SCOPE_LINK); } else if (fib_validate_source(saddr, 0, tos, 0, - dev, &spec_dst, &itag) < 0) + dev, &spec_dst, &itag, our) < 0) goto e_inval; rth = dst_alloc(&ipv4_dst_ops); @@ -1367,7 +1367,7 @@ int result; result = fib_validate_source(saddr, daddr, tos, loopback_dev.ifindex, - dev, &spec_dst, &itag); + dev, &spec_dst, &itag, 1); if (result < 0) goto martian_source; if (result) @@ -1394,7 +1394,7 @@ } err = fib_validate_source(saddr, daddr, tos, FIB_RES_OIF(res), dev, - &spec_dst, &itag); + &spec_dst, &itag, 0); if (err < 0) goto martian_source; @@ -1478,7 +1478,7 @@ spec_dst = inet_select_addr(dev, 0, RT_SCOPE_LINK); else { err = fib_validate_source(saddr, 0, tos, 0, dev, &spec_dst, - &itag); + &itag, 1); if (err < 0) goto martian_source; if (err) --- v2.4.5/linux/Documentation/filesystems/proc.txt~ Sun Jul 1 11:05:03 2001 +++ linux/Documentation/filesystems/proc.txt Sun Jul 1 14:28:21 2001 @@ -1561,6 +1561,18 @@ (external addresses can still be spoofed), without the need for additional firewall rules. +forward_shared +-------------- + +Integer value determines if a source validation should allow forwarding +of packets with local source address. 1 means yes, 0 means no. By default +the flag is disabled and such packets are not forwarded. + +If you enable this flag on internal network, the router will forward +packets from internal hosts with shared IP addresses no matter how +the rp_filter is set. This flag is activated only if it is enabled +both in specific device section and in "all" section. + secure_redirects ---------------- --- v2.4.5/linux/Documentation/networking/ip-sysctl.txt~ Sun Jul 1 11:05:34 2001 +++ linux/Documentation/networking/ip-sysctl.txt Sun Jul 1 14:29:03 2001 @@ -347,6 +347,17 @@ forwarding - BOOLEAN Enable IP forwarding on this interface. +forward_shared - BOOLEAN + Integer value determines if a source validation should allow + forwarding of packets with local source address. 1 means yes, + 0 means no. By default the flag is disabled and such packets + are not forwarded. + + If you enable this flag on internal network, the router will forward + packets from internal hosts with shared IP addresses no matter how + the rp_filter is set. This flag is activated only if it is + enabled both in specific device section and in "all" section. + mc_forwarding - BOOLEAN Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE and a multicast routing daemon is required.