--- /dev/null
+/* (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");
Code Review / kvmfornfv.git / blobdiff