Commit e110861f authored by Lorenzo Colitti's avatar Lorenzo Colitti Committed by David S. Miller
Browse files

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: default avatarLorenzo Colitti <lorenzo@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 87e067cd

include/net/ip.h

+3 −0
Original line number Diff line number Diff line
@@ -231,6 +231,9 @@ void ipfrag_init(void); 


void ip_static_sysctl_init(void);



#define IP4_REPLY_MARK(net, mark) \

	((net)->ipv4.sysctl_fwmark_reflect ? (mark) : 0)



static inline bool ip_is_fragment(const struct iphdr *iph)

{

	return (iph->frag_off & htons(IP_MF | IP_OFFSET)) != 0;

include/net/ipv6.h

+3 −0
Original line number Diff line number Diff line
@@ -113,6 +113,9 @@ struct frag_hdr { 
#define	IP6_MF		0x0001

#define	IP6_OFFSET	0xFFF8



#define IP6_REPLY_MARK(net, mark) \

	((net)->ipv6.sysctl.fwmark_reflect ? (mark) : 0)



#include <net/sock.h>



/* sysctls */

include/net/netns/ipv4.h

+2 −0
Original line number Diff line number Diff line
@@ -77,6 +77,8 @@ struct netns_ipv4 { 
	int sysctl_ip_no_pmtu_disc;

	int sysctl_ip_fwd_use_pmtu;



	int sysctl_fwmark_reflect;



	struct ping_group_range ping_group_range;



	atomic_t dev_addr_genid;

include/net/netns/ipv6.h

+1 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ struct netns_sysctl_ipv6 { 
	int flowlabel_consistency;

	int icmpv6_time;

	int anycast_src_echo_reply;

	int fwmark_reflect;

};



struct netns_ipv6 {

net/ipv4/icmp.c

+9 −2
Original line number Diff line number Diff line
@@ -337,6 +337,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 
	struct sock *sk;

	struct inet_sock *inet;

	__be32 daddr, saddr;

	u32 mark = IP4_REPLY_MARK(net, skb->mark);



	if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb))

		return;
@@ -349,6 +350,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 
	icmp_param->data.icmph.checksum = 0;



	inet->tos = ip_hdr(skb)->tos;

	sk->sk_mark = mark;

	daddr = ipc.addr = ip_hdr(skb)->saddr;

	saddr = fib_compute_spec_dst(skb);

	ipc.opt = NULL;
@@ -364,6 +366,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 
	memset(&fl4, 0, sizeof(fl4));

	fl4.daddr = daddr;

	fl4.saddr = saddr;

	fl4.flowi4_mark = mark;

	fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);

	fl4.flowi4_proto = IPPROTO_ICMP;

	security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
@@ -382,7 +385,7 @@ static struct rtable *icmp_route_lookup(struct net *net, 
					struct flowi4 *fl4,

					struct sk_buff *skb_in,

					const struct iphdr *iph,

					__be32 saddr, u8 tos,

					__be32 saddr, u8 tos, u32 mark,

					int type, int code,

					struct icmp_bxm *param)

{
@@ -394,6 +397,7 @@ static struct rtable *icmp_route_lookup(struct net *net, 
	fl4->daddr = (param->replyopts.opt.opt.srr ?

		      param->replyopts.opt.opt.faddr : iph->saddr);

	fl4->saddr = saddr;

	fl4->flowi4_mark = mark;

	fl4->flowi4_tos = RT_TOS(tos);

	fl4->flowi4_proto = IPPROTO_ICMP;

	fl4->fl4_icmp_type = type;
@@ -491,6 +495,7 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 
	struct flowi4 fl4;

	__be32 saddr;

	u8  tos;

	u32 mark;

	struct net *net;

	struct sock *sk;
@@ -592,6 +597,7 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 
	tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |

					   IPTOS_PREC_INTERNETCONTROL) :

					  iph->tos;

	mark = IP4_REPLY_MARK(net, skb_in->mark);



	if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb_in))

		goto out_unlock;
@@ -608,13 +614,14 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 
	icmp_param->skb	  = skb_in;

	icmp_param->offset = skb_network_offset(skb_in);

	inet_sk(sk)->tos = tos;

	sk->sk_mark = mark;

	ipc.addr = iph->saddr;

	ipc.opt = &icmp_param->replyopts.opt;

	ipc.tx_flags = 0;

	ipc.ttl = 0;

	ipc.tos = -1;



	rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos,

	rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,

			       type, code, icmp_param);

	if (IS_ERR(rt))

		goto out_unlock;

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