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netfilter: move nf_send_resetX() code to nf_reject_ipvX modules
Move nf_send_reset() and nf_send_reset6() to nf_reject_ipv4 and nf_reject_ipv6 respectively. This code is shared by x_tables and nf_tables. Signed-off-by: Pablo Neira Ayuso <[email protected]>
1 parent 51b0a5d commit c8d7b98

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7 files changed

+309
-117
lines changed

7 files changed

+309
-117
lines changed

‎include/net/netfilter/ipv4/nf_reject.h

Lines changed: 1 addition & 117 deletions
Original file line numberDiff line numberDiff line change
@@ -1,129 +1,13 @@
11
#ifndef _IPV4_NF_REJECT_H
22
#define _IPV4_NF_REJECT_H
33

4-
#include <net/ip.h>
5-
#include <net/tcp.h>
6-
#include <net/route.h>
7-
#include <net/dst.h>
84
#include <net/icmp.h>
95

106
static inline void nf_send_unreach(struct sk_buff *skb_in, int code)
117
{
128
icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
139
}
1410

15-
/* Send RST reply */
16-
static void nf_send_reset(struct sk_buff *oldskb, int hook)
17-
{
18-
struct sk_buff *nskb;
19-
const struct iphdr *oiph;
20-
struct iphdr *niph;
21-
const struct tcphdr *oth;
22-
struct tcphdr _otcph, *tcph;
23-
24-
/* IP header checks: fragment. */
25-
if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
26-
return;
27-
28-
oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
29-
sizeof(_otcph), &_otcph);
30-
if (oth == NULL)
31-
return;
32-
33-
/* No RST for RST. */
34-
if (oth->rst)
35-
return;
36-
37-
if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
38-
return;
39-
40-
/* Check checksum */
41-
if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
42-
return;
43-
oiph = ip_hdr(oldskb);
44-
45-
nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
46-
LL_MAX_HEADER, GFP_ATOMIC);
47-
if (!nskb)
48-
return;
49-
50-
skb_reserve(nskb, LL_MAX_HEADER);
51-
52-
skb_reset_network_header(nskb);
53-
niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
54-
niph->version = 4;
55-
niph->ihl = sizeof(struct iphdr) / 4;
56-
niph->tos = 0;
57-
niph->id = 0;
58-
niph->frag_off = htons(IP_DF);
59-
niph->protocol = IPPROTO_TCP;
60-
niph->check = 0;
61-
niph->saddr = oiph->daddr;
62-
niph->daddr = oiph->saddr;
63-
64-
skb_reset_transport_header(nskb);
65-
tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
66-
memset(tcph, 0, sizeof(*tcph));
67-
tcph->source = oth->dest;
68-
tcph->dest = oth->source;
69-
tcph->doff = sizeof(struct tcphdr) / 4;
70-
71-
if (oth->ack)
72-
tcph->seq = oth->ack_seq;
73-
else {
74-
tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
75-
oldskb->len - ip_hdrlen(oldskb) -
76-
(oth->doff << 2));
77-
tcph->ack = 1;
78-
}
79-
80-
tcph->rst = 1;
81-
tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr,
82-
niph->daddr, 0);
83-
nskb->ip_summed = CHECKSUM_PARTIAL;
84-
nskb->csum_start = (unsigned char *)tcph - nskb->head;
85-
nskb->csum_offset = offsetof(struct tcphdr, check);
86-
87-
/* ip_route_me_harder expects skb->dst to be set */
88-
skb_dst_set_noref(nskb, skb_dst(oldskb));
89-
90-
nskb->protocol = htons(ETH_P_IP);
91-
if (ip_route_me_harder(nskb, RTN_UNSPEC))
92-
goto free_nskb;
93-
94-
niph->ttl = ip4_dst_hoplimit(skb_dst(nskb));
95-
96-
/* "Never happens" */
97-
if (nskb->len > dst_mtu(skb_dst(nskb)))
98-
goto free_nskb;
99-
100-
nf_ct_attach(nskb, oldskb);
101-
102-
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
103-
/* If we use ip_local_out for bridged traffic, the MAC source on
104-
* the RST will be ours, instead of the destination's. This confuses
105-
* some routers/firewalls, and they drop the packet. So we need to
106-
* build the eth header using the original destination's MAC as the
107-
* source, and send the RST packet directly.
108-
*/
109-
if (oldskb->nf_bridge) {
110-
struct ethhdr *oeth = eth_hdr(oldskb);
111-
nskb->dev = oldskb->nf_bridge->physindev;
112-
niph->tot_len = htons(nskb->len);
113-
ip_send_check(niph);
114-
if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
115-
oeth->h_source, oeth->h_dest, nskb->len) < 0)
116-
goto free_nskb;
117-
dev_queue_xmit(nskb);
118-
} else
119-
#endif
120-
ip_local_out(nskb);
121-
122-
return;
123-
124-
free_nskb:
125-
kfree_skb(nskb);
126-
}
127-
11+
void nf_send_reset(struct sk_buff *oldskb, int hook);
12812

12913
#endif /* _IPV4_NF_REJECT_H */

‎net/ipv4/netfilter/Kconfig

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -61,8 +61,13 @@ config NFT_CHAIN_ROUTE_IPV4
6161
fields such as the source, destination, type of service and
6262
the packet mark.
6363

64+
config NF_REJECT_IPV4
65+
tristate "IPv4 packet rejection"
66+
default m if NETFILTER_ADVANCED=n
67+
6468
config NFT_REJECT_IPV4
6569
depends on NF_TABLES_IPV4
70+
select NF_REJECT_IPV4
6671
default NFT_REJECT
6772
tristate
6873

@@ -208,6 +213,7 @@ config IP_NF_FILTER
208213
config IP_NF_TARGET_REJECT
209214
tristate "REJECT target support"
210215
depends on IP_NF_FILTER
216+
select NF_REJECT_IPV4
211217
default m if NETFILTER_ADVANCED=n
212218
help
213219
The REJECT target allows a filtering rule to specify that an ICMP

‎net/ipv4/netfilter/Makefile

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -23,6 +23,9 @@ obj-$(CONFIG_NF_DEFRAG_IPV4) += nf_defrag_ipv4.o
2323
obj-$(CONFIG_NF_LOG_ARP) += nf_log_arp.o
2424
obj-$(CONFIG_NF_LOG_IPV4) += nf_log_ipv4.o
2525

26+
# reject
27+
obj-$(CONFIG_NF_REJECT_IPV4) += nf_reject_ipv4.o
28+
2629
# NAT helpers (nf_conntrack)
2730
obj-$(CONFIG_NF_NAT_H323) += nf_nat_h323.o
2831
obj-$(CONFIG_NF_NAT_PPTP) += nf_nat_pptp.o

‎net/ipv4/netfilter/nf_reject_ipv4.c

Lines changed: 127 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,127 @@
1+
/* (C) 1999-2001 Paul `Rusty' Russell
2+
* (C) 2002-2004 Netfilter Core Team <[email protected]>
3+
*
4+
* This program is free software; you can redistribute it and/or modify
5+
* it under the terms of the GNU General Public License version 2 as
6+
* published by the Free Software Foundation.
7+
*/
8+
9+
#include <net/ip.h>
10+
#include <net/tcp.h>
11+
#include <net/route.h>
12+
#include <net/dst.h>
13+
#include <linux/netfilter_ipv4.h>
14+
15+
/* Send RST reply */
16+
void nf_send_reset(struct sk_buff *oldskb, int hook)
17+
{
18+
struct sk_buff *nskb;
19+
const struct iphdr *oiph;
20+
struct iphdr *niph;
21+
const struct tcphdr *oth;
22+
struct tcphdr _otcph, *tcph;
23+
24+
/* IP header checks: fragment. */
25+
if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
26+
return;
27+
28+
oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
29+
sizeof(_otcph), &_otcph);
30+
if (oth == NULL)
31+
return;
32+
33+
/* No RST for RST. */
34+
if (oth->rst)
35+
return;
36+
37+
if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
38+
return;
39+
40+
/* Check checksum */
41+
if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
42+
return;
43+
oiph = ip_hdr(oldskb);
44+
45+
nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
46+
LL_MAX_HEADER, GFP_ATOMIC);
47+
if (!nskb)
48+
return;
49+
50+
skb_reserve(nskb, LL_MAX_HEADER);
51+
52+
skb_reset_network_header(nskb);
53+
niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
54+
niph->version = 4;
55+
niph->ihl = sizeof(struct iphdr) / 4;
56+
niph->tos = 0;
57+
niph->id = 0;
58+
niph->frag_off = htons(IP_DF);
59+
niph->protocol = IPPROTO_TCP;
60+
niph->check = 0;
61+
niph->saddr = oiph->daddr;
62+
niph->daddr = oiph->saddr;
63+
64+
skb_reset_transport_header(nskb);
65+
tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
66+
memset(tcph, 0, sizeof(*tcph));
67+
tcph->source = oth->dest;
68+
tcph->dest = oth->source;
69+
tcph->doff = sizeof(struct tcphdr) / 4;
70+
71+
if (oth->ack)
72+
tcph->seq = oth->ack_seq;
73+
else {
74+
tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
75+
oldskb->len - ip_hdrlen(oldskb) -
76+
(oth->doff << 2));
77+
tcph->ack = 1;
78+
}
79+
80+
tcph->rst = 1;
81+
tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr,
82+
niph->daddr, 0);
83+
nskb->ip_summed = CHECKSUM_PARTIAL;
84+
nskb->csum_start = (unsigned char *)tcph - nskb->head;
85+
nskb->csum_offset = offsetof(struct tcphdr, check);
86+
87+
/* ip_route_me_harder expects skb->dst to be set */
88+
skb_dst_set_noref(nskb, skb_dst(oldskb));
89+
90+
nskb->protocol = htons(ETH_P_IP);
91+
if (ip_route_me_harder(nskb, RTN_UNSPEC))
92+
goto free_nskb;
93+
94+
niph->ttl = ip4_dst_hoplimit(skb_dst(nskb));
95+
96+
/* "Never happens" */
97+
if (nskb->len > dst_mtu(skb_dst(nskb)))
98+
goto free_nskb;
99+
100+
nf_ct_attach(nskb, oldskb);
101+
102+
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
103+
/* If we use ip_local_out for bridged traffic, the MAC source on
104+
* the RST will be ours, instead of the destination's. This confuses
105+
* some routers/firewalls, and they drop the packet. So we need to
106+
* build the eth header using the original destination's MAC as the
107+
* source, and send the RST packet directly.
108+
*/
109+
if (oldskb->nf_bridge) {
110+
struct ethhdr *oeth = eth_hdr(oldskb);
111+
nskb->dev = oldskb->nf_bridge->physindev;
112+
niph->tot_len = htons(nskb->len);
113+
ip_send_check(niph);
114+
if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
115+
oeth->h_source, oeth->h_dest, nskb->len) < 0)
116+
goto free_nskb;
117+
dev_queue_xmit(nskb);
118+
} else
119+
#endif
120+
ip_local_out(nskb);
121+
122+
return;
123+
124+
free_nskb:
125+
kfree_skb(nskb);
126+
}
127+
EXPORT_SYMBOL_GPL(nf_send_reset);

‎net/ipv6/netfilter/Kconfig

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -40,8 +40,13 @@ config NFT_CHAIN_ROUTE_IPV6
4040
fields such as the source, destination, flowlabel, hop-limit and
4141
the packet mark.
4242

43+
config NF_REJECT_IPV6
44+
tristate "IPv6 packet rejection"
45+
default m if NETFILTER_ADVANCED=n
46+
4347
config NFT_REJECT_IPV6
4448
depends on NF_TABLES_IPV6
49+
select NF_REJECT_IPV6
4550
default NFT_REJECT
4651
tristate
4752

@@ -208,6 +213,7 @@ config IP6_NF_FILTER
208213
config IP6_NF_TARGET_REJECT
209214
tristate "REJECT target support"
210215
depends on IP6_NF_FILTER
216+
select NF_REJECT_IPV6
211217
default m if NETFILTER_ADVANCED=n
212218
help
213219
The REJECT target allows a filtering rule to specify that an ICMPv6

‎net/ipv6/netfilter/Makefile

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,9 @@ obj-$(CONFIG_NF_DEFRAG_IPV6) += nf_defrag_ipv6.o
2727
# logging
2828
obj-$(CONFIG_NF_LOG_IPV6) += nf_log_ipv6.o
2929

30+
# reject
31+
obj-$(CONFIG_NF_REJECT_IPV6) += nf_reject_ipv6.o
32+
3033
# nf_tables
3134
obj-$(CONFIG_NF_TABLES_IPV6) += nf_tables_ipv6.o
3235
obj-$(CONFIG_NFT_CHAIN_ROUTE_IPV6) += nft_chain_route_ipv6.o

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