net: add a sysctl to reflect the fwmark on replies

Kernel-originated IP packets that have no user socket associated
with them (e.g., ICMP errors and echo replies, TCP RSTs, etc.)
are emitted with a mark of zero. Add a sysctl to make them have
the same mark as the packet they are replying to.

This allows an administrator that wishes to do so to use
mark-based routing, firewalling, etc. for these replies by
marking the original packets inbound.

Tested using user-mode linux:
 - ICMP/ICMPv6 echo replies and errors.
 - TCP RST packets (IPv4 and IPv6).

Signed-off-by: Lorenzo Colitti <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Lorenzo Colitti 2014-05-13 10:17:33 -07:00 • committed by David S. Miller
commit e110861f86
10 changed files with 41 additions and 3 deletions

View file

@ -400,6 +400,7 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
int len;
int hlimit;
int err = 0;
u32 mark = IP6_REPLY_MARK(net, skb->mark);
if ((u8 *)hdr < skb->head ||
(skb_network_header(skb) + sizeof(*hdr)) > skb_tail_pointer(skb))
@ -466,6 +467,7 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
fl6.daddr = hdr->saddr;
if (saddr)
fl6.saddr = *saddr;
fl6.flowi6_mark = mark;
fl6.flowi6_oif = iif;
fl6.fl6_icmp_type = type;
fl6.fl6_icmp_code = code;
@ -474,6 +476,7 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
sk = icmpv6_xmit_lock(net);
if (sk == NULL)
return;
sk->sk_mark = mark;
np = inet6_sk(sk);
if (!icmpv6_xrlim_allow(sk, type, &fl6))
@ -551,6 +554,7 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
int err = 0;
int hlimit;
u8 tclass;
u32 mark = IP6_REPLY_MARK(net, skb->mark);
saddr = &ipv6_hdr(skb)->daddr;
@ -569,11 +573,13 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
fl6.saddr = *saddr;
fl6.flowi6_oif = skb->dev->ifindex;
fl6.fl6_icmp_type = ICMPV6_ECHO_REPLY;
fl6.flowi6_mark = mark;
security_skb_classify_flow(skb, flowi6_to_flowi(&fl6));
sk = icmpv6_xmit_lock(net);
if (sk == NULL)
return;
sk->sk_mark = mark;
np = inet6_sk(sk);
if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))

View file

@ -38,6 +38,13 @@ static struct ctl_table ipv6_table_template[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "fwmark_reflect",
.data = &init_net.ipv6.sysctl.fwmark_reflect,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{ }
};

View file

@ -812,6 +812,7 @@ static void tcp_v6_send_response(struct sk_buff *skb, u32 seq, u32 ack, u32 win,
fl6.flowi6_oif = inet6_iif(skb);
else
fl6.flowi6_oif = oif;
fl6.flowi6_mark = IP6_REPLY_MARK(net, skb->mark);
fl6.fl6_dport = t1->dest;
fl6.fl6_sport = t1->source;
security_skb_classify_flow(skb, flowi6_to_flowi(&fl6));