diff options
Diffstat (limited to 'kernel/net/ipv4/netfilter/nf_reject_ipv4.c')
| -rw-r--r-- | kernel/net/ipv4/netfilter/nf_reject_ipv4.c | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/kernel/net/ipv4/netfilter/nf_reject_ipv4.c b/kernel/net/ipv4/netfilter/nf_reject_ipv4.c new file mode 100644 index 000000000..3262e41ff --- /dev/null +++ b/kernel/net/ipv4/netfilter/nf_reject_ipv4.c @@ -0,0 +1,192 @@ +/* (C) 1999-2001 Paul `Rusty' Russell + * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/module.h> +#include <net/ip.h> +#include <net/tcp.h> +#include <net/route.h> +#include <net/dst.h> +#include <net/netfilter/ipv4/nf_reject.h> +#include <linux/netfilter_ipv4.h> +#include <linux/netfilter_bridge.h> +#include <net/netfilter/ipv4/nf_reject.h> + +const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb, + struct tcphdr *_oth, int hook) +{ + const struct tcphdr *oth; + + /* IP header checks: fragment. */ + if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET)) + return NULL; + + oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb), + sizeof(struct tcphdr), _oth); + if (oth == NULL) + return NULL; + + /* No RST for RST. */ + if (oth->rst) + return NULL; + + /* Check checksum */ + if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP)) + return NULL; + + return oth; +} +EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get); + +struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb, + const struct sk_buff *oldskb, + __u8 protocol, int ttl) +{ + struct iphdr *niph, *oiph = ip_hdr(oldskb); + + skb_reset_network_header(nskb); + niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr)); + niph->version = 4; + niph->ihl = sizeof(struct iphdr) / 4; + niph->tos = 0; + niph->id = 0; + niph->frag_off = htons(IP_DF); + niph->protocol = protocol; + niph->check = 0; + niph->saddr = oiph->daddr; + niph->daddr = oiph->saddr; + niph->ttl = ttl; + + nskb->protocol = htons(ETH_P_IP); + + return niph; +} +EXPORT_SYMBOL_GPL(nf_reject_iphdr_put); + +void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *oldskb, + const struct tcphdr *oth) +{ + struct iphdr *niph = ip_hdr(nskb); + struct tcphdr *tcph; + + skb_reset_transport_header(nskb); + tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); + memset(tcph, 0, sizeof(*tcph)); + tcph->source = oth->dest; + tcph->dest = oth->source; + tcph->doff = sizeof(struct tcphdr) / 4; + + if (oth->ack) { + tcph->seq = oth->ack_seq; + } else { + tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin + + oldskb->len - ip_hdrlen(oldskb) - + (oth->doff << 2)); + tcph->ack = 1; + } + + tcph->rst = 1; + tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr, + niph->daddr, 0); + nskb->ip_summed = CHECKSUM_PARTIAL; + nskb->csum_start = (unsigned char *)tcph - nskb->head; + nskb->csum_offset = offsetof(struct tcphdr, check); +} +EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put); + +/* Send RST reply */ +void nf_send_reset(struct sk_buff *oldskb, int hook) +{ + struct sk_buff *nskb; + const struct iphdr *oiph; + struct iphdr *niph; + const struct tcphdr *oth; + struct tcphdr _oth; + + oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook); + if (!oth) + return; + + if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) + return; + + oiph = ip_hdr(oldskb); + + nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) + + LL_MAX_HEADER, GFP_ATOMIC); + if (!nskb) + return; + + /* ip_route_me_harder expects skb->dst to be set */ + skb_dst_set_noref(nskb, skb_dst(oldskb)); + + skb_reserve(nskb, LL_MAX_HEADER); + niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP, + ip4_dst_hoplimit(skb_dst(nskb))); + nf_reject_ip_tcphdr_put(nskb, oldskb, oth); + + if (ip_route_me_harder(nskb, RTN_UNSPEC)) + goto free_nskb; + + /* "Never happens" */ + if (nskb->len > dst_mtu(skb_dst(nskb))) + goto free_nskb; + + nf_ct_attach(nskb, oldskb); + +#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) + /* If we use ip_local_out for bridged traffic, the MAC source on + * the RST will be ours, instead of the destination's. This confuses + * some routers/firewalls, and they drop the packet. So we need to + * build the eth header using the original destination's MAC as the + * source, and send the RST packet directly. + */ + if (oldskb->nf_bridge) { + struct ethhdr *oeth = eth_hdr(oldskb); + + nskb->dev = nf_bridge_get_physindev(oldskb); + niph->tot_len = htons(nskb->len); + ip_send_check(niph); + if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol), + oeth->h_source, oeth->h_dest, nskb->len) < 0) + goto free_nskb; + dev_queue_xmit(nskb); + } else +#endif + ip_local_out(nskb); + + return; + + free_nskb: + kfree_skb(nskb); +} +EXPORT_SYMBOL_GPL(nf_send_reset); + +void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) +{ + struct iphdr *iph = ip_hdr(skb_in); + u8 proto; + + if (skb_in->csum_bad || iph->frag_off & htons(IP_OFFSET)) + return; + + if (skb_csum_unnecessary(skb_in)) { + icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); + return; + } + + if (iph->protocol == IPPROTO_TCP || iph->protocol == IPPROTO_UDP) + proto = iph->protocol; + else + proto = 0; + + if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0) + icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); +} +EXPORT_SYMBOL_GPL(nf_send_unreach); + +MODULE_LICENSE("GPL"); |