diff options
Diffstat (limited to 'net/ipv4/ip_forward.c')
| -rw-r--r-- | net/ipv4/ip_forward.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c new file mode 100644 index 00000000..977a805c --- /dev/null +++ b/net/ipv4/ip_forward.c @@ -0,0 +1,203 @@ +/* + * INET An implementation of the TCP/IP protocol suite for the LINUX + * operating system. INET is implemented using the BSD Socket + * interface as the means of communication with the user level. + * + * The IP forwarding functionality. + * + * Authors: see ip.c + * + * Fixes: + * Many : Split from ip.c , see ip_input.c for + * history. + * Dave Gregorich : NULL ip_rt_put fix for multicast + * routing. + * Jos Vos : Add call_out_firewall before sending, + * use output device for accounting. + * Jos Vos : Call forward firewall after routing + * (always use output device). + * Mike McLagan : Routing by source + */ + +#include <linux/types.h> +#include <linux/mm.h> +#include <linux/skbuff.h> +#include <linux/ip.h> +#include <linux/icmp.h> +#include <linux/netdevice.h> +#include <linux/slab.h> +#include <net/sock.h> +#include <net/ip.h> +#include <net/tcp.h> +#include <net/udp.h> +#include <net/icmp.h> +#include <linux/tcp.h> +#include <linux/udp.h> +#include <linux/netfilter_ipv4.h> +#include <net/checksum.h> +#include <linux/route.h> +#include <net/route.h> +#include <net/xfrm.h> + +static bool ip_may_fragment(const struct sk_buff *skb) +{ + return unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0) || + skb->local_df; +} + +static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu) +{ + if (skb->len <= mtu) + return false; + + if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu) + return false; + + return true; +} + +static bool ip_gso_exceeds_dst_mtu(const struct sk_buff *skb) +{ + unsigned int mtu; + + if (skb->local_df || !skb_is_gso(skb)) + return false; + + mtu = dst_mtu(skb_dst(skb)); + + /* if seglen > mtu, do software segmentation for IP fragmentation on + * output. DF bit cannot be set since ip_forward would have sent + * icmp error. + */ + return skb_gso_network_seglen(skb) > mtu; +} + +/* called if GSO skb needs to be fragmented on forward */ +static int ip_forward_finish_gso(struct sk_buff *skb) +{ + struct dst_entry *dst = skb_dst(skb); + netdev_features_t features; + struct sk_buff *segs; + int ret = 0; + + features = netif_skb_dev_features(skb, dst->dev); + segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK); + if (IS_ERR(segs)) { + kfree_skb(skb); + return -ENOMEM; + } + + consume_skb(skb); + + do { + struct sk_buff *nskb = segs->next; + int err; + + segs->next = NULL; + err = dst_output(segs); + + if (err && ret == 0) + ret = err; + segs = nskb; + } while (segs); + + return ret; +} + +static int ip_forward_finish(struct sk_buff *skb) +{ + struct ip_options *opt = &(IPCB(skb)->opt); + + IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS); + IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len); + + if (unlikely(opt->optlen)) + ip_forward_options(skb); + + if (ip_gso_exceeds_dst_mtu(skb)) + return ip_forward_finish_gso(skb); + + return dst_output(skb); +} + +int ip_forward(struct sk_buff *skb) +{ + struct iphdr *iph; /* Our header */ + struct rtable *rt; /* Route we use */ + struct ip_options *opt = &(IPCB(skb)->opt); + + if (skb_warn_if_lro(skb)) + goto drop; + + if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb)) + goto drop; + + if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb)) + return NET_RX_SUCCESS; + + if (skb->pkt_type != PACKET_HOST) + goto drop; + + skb_forward_csum(skb); + + /* + * According to the RFC, we must first decrease the TTL field. If + * that reaches zero, we must reply an ICMP control message telling + * that the packet's lifetime expired. + */ + if (ip_hdr(skb)->ttl <= 1) + goto too_many_hops; + + if (!xfrm4_route_forward(skb)) + goto drop; + + rt = skb_rtable(skb); + + if (opt->is_strictroute && rt->rt_uses_gateway) + goto sr_failed; + + /* avoid to ping some website failed, because they set IP_DF flag*/ +#if 0 + if (unlikely(skb->len > dst_mtu(&rt->dst) && !skb_is_gso(skb) && + (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) { + IP_INC_STATS(dev_net(rt->dst.dev), IPSTATS_MIB_FRAGFAILS); + icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, + htonl(dst_mtu(&rt->dst))); + goto drop; + } +#endif + /* We are about to mangle packet. Copy it! */ + if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len)) + goto drop; + iph = ip_hdr(skb); + + /* Decrease ttl after skb cow done */ + ip_decrease_ttl(iph); + + /* + * We now generate an ICMP HOST REDIRECT giving the route + * we calculated. + */ + if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb_sec_path(skb)) + ip_rt_send_redirect(skb); + + skb->priority = rt_tos2priority(iph->tos); + + return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, skb, skb->dev, + rt->dst.dev, ip_forward_finish); + +sr_failed: + /* + * Strict routing permits no gatewaying + */ + icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0); + goto drop; + +too_many_hops: + /* Tell the sender its packet died... */ + IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_INHDRERRORS); + icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0); +drop: + kfree_skb(skb); + return NET_RX_DROP; +} |