1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
|
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Pablo Neira Ayuso <pablo@netfilter.org>,
netfilter-devel@vger.kernel.org, netdev@vger.kernel.org
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: [PATCH nf 2/2] netfilter: use actual socket sk rather than skb sk when routing harder
Date: Thu, 29 Oct 2020 03:56:06 +0100
Message-ID: <20201029025606.3523771-3-Jason@zx2c4.com> (raw)
In-Reply-To: <20201029025606.3523771-1-Jason@zx2c4.com>
If netfilter changes the packet mark when mangling, the packet is
rerouted using the route_me_harder set of functions. Prior to this
commit, there's one big difference between route_me_harder and the
ordinary initial routing functions, described in the comment above
__ip_queue_xmit():
/* Note: skb->sk can be different from sk, in case of tunnels */
int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
That function goes on to correctly make use of sk->sk_bound_dev_if,
rather than skb->sk->sk_bound_dev_if. And indeed the comment is true: a
tunnel will receive a packet in ndo_start_xmit with an initial skb->sk.
It will make some transformations to that packet, and then it will send
the encapsulated packet out of a *new* socket. That new socket will
basically always have a different sk_bound_dev_if (otherwise there'd be
a routing loop). So for the purposes of routing the encapsulated packet,
the routing information as it pertains to the socket should come from
that socket's sk, rather than the packet's original skb->sk. For that
reason __ip_queue_xmit() and related functions all do the right thing.
One might argue that all tunnels should just call skb_orphan(skb) before
transmitting the encapsulated packet into the new socket. But tunnels do
*not* do this -- and this is wisely avoided in skb_scrub_packet() too --
because features like TSQ rely on skb->destructor() being called when
that buffer space is truely available again. Calling skb_orphan(skb) too
early would result in buffers filling up unnecessarily and accounting
info being all wrong. Instead, additional routing must take into account
the new sk, just as __ip_queue_xmit() notes.
So, this commit addresses the problem by fishing the correct sk out of
state->sk -- it's already set properly in the call to nf_hook() in
__ip_local_out(), which receives the sk as part of its normal
functionality. So we make sure to plumb state->sk through the various
route_me_harder functions, and then make correct use of it following the
example of __ip_queue_xmit().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
[aaronjg@stanford.edu: backported to 4.14]
Signed-off-by: Aaron Goodman <aaronjg@stanford.edu>
--- a/include/linux/netfilter_ipv4.h
+++ b/include/linux/netfilter_ipv4.h
@@ -16,7 +16,7 @@ struct ip_rt_info {
u_int32_t mark;
};
-int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned addr_type);
+int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned addr_type);
struct nf_queue_entry;
--- a/include/linux/netfilter_ipv6.h
+++ b/include/linux/netfilter_ipv6.h
@@ -41,7 +41,7 @@ struct nf_ipv6_ops {
};
#ifdef CONFIG_NETFILTER
-int ip6_route_me_harder(struct net *net, struct sk_buff *skb);
+int ip6_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb);
__sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
unsigned int dataoff, u_int8_t protocol);
--- a/net/ipv4/netfilter.c
+++ b/net/ipv4/netfilter.c
@@ -17,17 +17,19 @@
#include <net/netfilter/nf_queue.h>
/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
-int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_type)
+int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned int addr_type)
{
const struct iphdr *iph = ip_hdr(skb);
struct rtable *rt;
struct flowi4 fl4 = {};
__be32 saddr = iph->saddr;
- const struct sock *sk = skb_to_full_sk(skb);
- __u8 flags = sk ? inet_sk_flowi_flags(sk) : 0;
+ __u8 flags;
struct net_device *dev = skb_dst(skb)->dev;
unsigned int hh_len;
+ sk = sk_to_full_sk(sk);
+ flags = sk ? inet_sk_flowi_flags(sk) : 0;
+
if (addr_type == RTN_UNSPEC)
addr_type = inet_addr_type_dev_table(net, dev, saddr);
if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
@@ -91,7 +93,7 @@ int nf_ip_reroute(struct sk_buff *skb, c
skb->mark == rt_info->mark &&
iph->daddr == rt_info->daddr &&
iph->saddr == rt_info->saddr))
- return ip_route_me_harder(entry->state.net, skb,
+ return ip_route_me_harder(entry->state.net, entry->state.sk, skb,
RTN_UNSPEC);
}
return 0;
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -53,7 +53,7 @@ synproxy_send_tcp(struct net *net,
skb_dst_set_noref(nskb, skb_dst(skb));
nskb->protocol = htons(ETH_P_IP);
- if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
+ if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
goto free_nskb;
if (nfct) {
--- a/net/ipv4/netfilter/iptable_mangle.c
+++ b/net/ipv4/netfilter/iptable_mangle.c
@@ -65,7 +65,7 @@ ipt_mangle_out(struct sk_buff *skb, cons
iph->daddr != daddr ||
skb->mark != mark ||
iph->tos != tos) {
- err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
+ err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
if (err < 0)
ret = NF_DROP_ERR(err);
}
--- a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
@@ -397,7 +397,7 @@ nf_nat_ipv4_local_fn(void *priv, struct
if (ct->tuplehash[dir].tuple.dst.u3.ip !=
ct->tuplehash[!dir].tuple.src.u3.ip) {
- err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
+ err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
if (err < 0)
ret = NF_DROP_ERR(err);
}
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -129,7 +129,7 @@ void nf_send_reset(struct net *net, stru
ip4_dst_hoplimit(skb_dst(nskb)));
nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
- if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
+ if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
goto free_nskb;
niph = ip_hdr(nskb);
--- a/net/ipv4/netfilter/nft_chain_route_ipv4.c
+++ b/net/ipv4/netfilter/nft_chain_route_ipv4.c
@@ -50,7 +50,7 @@ static unsigned int nf_route_table_hook(
iph->daddr != daddr ||
skb->mark != mark ||
iph->tos != tos) {
- err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
+ err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
if (err < 0)
ret = NF_DROP_ERR(err);
}
--- a/net/ipv6/netfilter.c
+++ b/net/ipv6/netfilter.c
@@ -18,10 +18,10 @@
#include <net/ip6_checksum.h>
#include <net/netfilter/nf_queue.h>
-int ip6_route_me_harder(struct net *net, struct sk_buff *skb)
+int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff *skb)
{
const struct ipv6hdr *iph = ipv6_hdr(skb);
- struct sock *sk = sk_to_full_sk(skb->sk);
+ struct sock *sk = sk_to_full_sk(sk_partial);
unsigned int hh_len;
struct dst_entry *dst;
int strict = (ipv6_addr_type(&iph->daddr) &
@@ -82,7 +82,7 @@ static int nf_ip6_reroute(struct sk_buff
if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
!ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
skb->mark != rt_info->mark)
- return ip6_route_me_harder(entry->state.net, skb);
+ return ip6_route_me_harder(entry->state.net, entry->state.sk, skb);
}
return 0;
}
--- a/net/ipv6/netfilter/ip6table_mangle.c
+++ b/net/ipv6/netfilter/ip6table_mangle.c
@@ -60,7 +60,7 @@ ip6t_mangle_out(struct sk_buff *skb, con
skb->mark != mark ||
ipv6_hdr(skb)->hop_limit != hop_limit ||
flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
- err = ip6_route_me_harder(state->net, skb);
+ err = ip6_route_me_harder(state->net, state->sk, skb);
if (err < 0)
ret = NF_DROP_ERR(err);
}
--- a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
@@ -414,7 +414,7 @@ nf_nat_ipv6_local_fn(void *priv, struct
if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
&ct->tuplehash[!dir].tuple.src.u3)) {
- err = ip6_route_me_harder(state->net, skb);
+ err = ip6_route_me_harder(state->net, state->sk, skb);
if (err < 0)
ret = NF_DROP_ERR(err);
}
--- a/net/ipv6/netfilter/nft_chain_route_ipv6.c
+++ b/net/ipv6/netfilter/nft_chain_route_ipv6.c
@@ -52,7 +52,7 @@ static unsigned int nf_route_table_hook(
skb->mark != mark ||
ipv6_hdr(skb)->hop_limit != hop_limit ||
flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
- err = ip6_route_me_harder(state->net, skb);
+ err = ip6_route_me_harder(state->net, state->sk, skb);
if (err < 0)
ret = NF_DROP_ERR(err);
}
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -713,12 +713,12 @@ static int ip_vs_route_me_harder(struct
struct dst_entry *dst = skb_dst(skb);
if (dst->dev && !(dst->dev->flags & IFF_LOOPBACK) &&
- ip6_route_me_harder(ipvs->net, skb) != 0)
+ ip6_route_me_harder(ipvs->net, skb->sk, skb) != 0)
return 1;
} else
#endif
if (!(skb_rtable(skb)->rt_flags & RTCF_LOCAL) &&
- ip_route_me_harder(ipvs->net, skb, RTN_LOCAL) != 0)
+ ip_route_me_harder(ipvs->net, skb->sk, skb, RTN_LOCAL) != 0)
return 1;
return 0;
|
