| #ifndef _IPV4_NF_REJECT_H |
| #define _IPV4_NF_REJECT_H |
| |
| #include <net/ip.h> |
| #include <net/tcp.h> |
| #include <net/route.h> |
| #include <net/dst.h> |
| |
| static inline void nf_send_unreach(struct sk_buff *skb_in, int code) |
| { |
| icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); |
| } |
| |
| /* Send RST reply */ |
| static 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 _otcph, *tcph; |
| |
| /* IP header checks: fragment. */ |
| if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET)) |
| return; |
| |
| oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb), |
| sizeof(_otcph), &_otcph); |
| if (oth == NULL) |
| return; |
| |
| /* No RST for RST. */ |
| if (oth->rst) |
| return; |
| |
| if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) |
| return; |
| |
| /* Check checksum */ |
| if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP)) |
| return; |
| oiph = ip_hdr(oldskb); |
| |
| nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) + |
| LL_MAX_HEADER, GFP_ATOMIC); |
| if (!nskb) |
| return; |
| |
| skb_reserve(nskb, LL_MAX_HEADER); |
| |
| 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 = IPPROTO_TCP; |
| niph->check = 0; |
| niph->saddr = oiph->daddr; |
| niph->daddr = oiph->saddr; |
| |
| 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); |
| |
| /* ip_route_me_harder expects skb->dst to be set */ |
| skb_dst_set_noref(nskb, skb_dst(oldskb)); |
| |
| nskb->protocol = htons(ETH_P_IP); |
| if (ip_route_me_harder(nskb, RTN_UNSPEC)) |
| goto free_nskb; |
| |
| niph->ttl = ip4_dst_hoplimit(skb_dst(nskb)); |
| |
| /* "Never happens" */ |
| if (nskb->len > dst_mtu(skb_dst(nskb))) |
| goto free_nskb; |
| |
| nf_ct_attach(nskb, oldskb); |
| |
| #ifdef 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 = oldskb->nf_bridge->physindev; |
| 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); |
| } |
| |
| |
| #endif /* _IPV4_NF_REJECT_H */ |