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route: add support for directed broadcast forwarding

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This patch implements the feature described in rfc1812#section-5.3.5.2
and rfc2644. It allows the router to forward directed broadcast when
sysctl bc_forwarding is enabled.

Note that this feature could be done by iptables -j TEE, but it would
cause some problems:
  - target TEE's gateway param has to be set with a specific address,
    and it's not flexible especially when the route wants forward all
    directed broadcasts.
  - this duplicates the directed broadcasts so this may cause side
    effects to applications.

Besides, to keep consistent with other os router like BSD, it's also
necessary to implement it in the route rx path.

Note that route cache needs to be flushed when bc_forwarding is
changed.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Long
2018-07-27 16:37:28 +08:00
committed by David S. Miller
parent d0c1f01138
commit 5cbf777cfd
5 changed files with 19 additions and 1 deletions
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11
net/ipv4/devinet.c
View File

@@ -1827,6 +1827,8 @@ static int inet_netconf_msgsize_devconf(int type)
size += nla_total_size(4);
if (all || type == NETCONFA_MC_FORWARDING)
size += nla_total_size(4);
if (all || type == NETCONFA_BC_FORWARDING)
size += nla_total_size(4);
if (all || type == NETCONFA_PROXY_NEIGH)
size += nla_total_size(4);
if (all || type == NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN)
@@ -1873,6 +1875,10 @@ static int inet_netconf_fill_devconf(struct sk_buff *skb, int ifindex,
nla_put_s32(skb, NETCONFA_MC_FORWARDING,
IPV4_DEVCONF(*devconf, MC_FORWARDING)) < 0)
goto nla_put_failure;
if ((all || type == NETCONFA_BC_FORWARDING) &&
nla_put_s32(skb, NETCONFA_BC_FORWARDING,
IPV4_DEVCONF(*devconf, BC_FORWARDING)) < 0)
goto nla_put_failure;
if ((all || type == NETCONFA_PROXY_NEIGH) &&
nla_put_s32(skb, NETCONFA_PROXY_NEIGH,
IPV4_DEVCONF(*devconf, PROXY_ARP)) < 0)
@@ -2143,6 +2149,10 @@ static int devinet_conf_proc(struct ctl_table *ctl, int write,
if ((new_value == 0) && (old_value != 0))
rt_cache_flush(net);
if (i == IPV4_DEVCONF_BC_FORWARDING - 1 &&
new_value != old_value)
rt_cache_flush(net);
if (i == IPV4_DEVCONF_RP_FILTER - 1 &&
new_value != old_value) {
ifindex = devinet_conf_ifindex(net, cnf);
@@ -2259,6 +2269,7 @@ static struct devinet_sysctl_table {
DEVINET_SYSCTL_COMPLEX_ENTRY(FORWARDING, "forwarding",
devinet_sysctl_forward),
DEVINET_SYSCTL_RO_ENTRY(MC_FORWARDING, "mc_forwarding"),
DEVINET_SYSCTL_RW_ENTRY(BC_FORWARDING, "bc_forwarding"),
DEVINET_SYSCTL_RW_ENTRY(ACCEPT_REDIRECTS, "accept_redirects"),
DEVINET_SYSCTL_RW_ENTRY(SECURE_REDIRECTS, "secure_redirects"),