/* * 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 Internet Protocol (IP) output module. * * Version: $Id: ip_output.c,v 1.67.2.1 1999/09/07 02:25:23 davem Exp $ * * Authors: Ross Biro, * Fred N. van Kempen, * Donald Becker, * Alan Cox, * Richard Underwood * Stefan Becker, * Jorge Cwik, * Arnt Gulbrandsen, * * See ip_input.c for original log * * Fixes: * Alan Cox : Missing nonblock feature in ip_build_xmit. * Mike Kilburn : htons() missing in ip_build_xmit. * Bradford Johnson: Fix faulty handling of some frames when * no route is found. * Alexander Demenshin: Missing sk/skb free in ip_queue_xmit * (in case if packet not accepted by * output firewall rules) * Mike McLagan : Routing by source * Alexey Kuznetsov: use new route cache * Andi Kleen: Fix broken PMTU recovery and remove * some redundant tests. * Vitaly E. Lavrov : Transparent proxy revived after year coma. * Andi Kleen : Replace ip_reply with ip_send_reply. * Andi Kleen : Split fast and slow ip_build_xmit path * for decreased register pressure on x86 * and more readibility. * Marc Boucher : When call_out_firewall returns FW_QUEUE, * silently drop skb instead of failing with -EPERM. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Shall we try to damage output packets if routing dev changes? */ int sysctl_ip_dynaddr = 0; int ip_id_count = 0; /* Generate a checksum for an outgoing IP datagram. */ __inline__ void ip_send_check(struct iphdr *iph) { iph->check = 0; iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl); } /* * Add an ip header to a skbuff and send it out. */ void ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk, u32 saddr, u32 daddr, struct ip_options *opt) { struct rtable *rt = (struct rtable *)skb->dst; struct iphdr *iph; struct device *dev; /* Build the IP header. */ if (opt) iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr) + opt->optlen); else iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr)); iph->version = 4; iph->ihl = 5; iph->tos = sk->ip_tos; iph->frag_off = 0; if (ip_dont_fragment(sk, &rt->u.dst)) iph->frag_off |= htons(IP_DF); iph->ttl = sk->ip_ttl; iph->daddr = rt->rt_dst; iph->saddr = rt->rt_src; iph->protocol = sk->protocol; iph->tot_len = htons(skb->len); iph->id = htons(ip_id_count++); skb->nh.iph = iph; if (opt && opt->optlen) { iph->ihl += opt->optlen>>2; ip_options_build(skb, opt, daddr, rt, 0); } dev = rt->u.dst.dev; #ifdef CONFIG_FIREWALL /* Now we have no better mechanism to notify about error. */ switch (call_out_firewall(PF_INET, dev, iph, NULL, &skb)) { case FW_REJECT: icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0); /* Fall thru... */ case FW_BLOCK: case FW_QUEUE: kfree_skb(skb); return; } #endif ip_send_check(iph); /* Send it out. */ skb->dst->output(skb); return; } int __ip_finish_output(struct sk_buff *skb) { return ip_finish_output(skb); } int ip_mc_output(struct sk_buff *skb) { struct sock *sk = skb->sk; struct rtable *rt = (struct rtable*)skb->dst; struct device *dev = rt->u.dst.dev; /* * If the indicated interface is up and running, send the packet. */ ip_statistics.IpOutRequests++; #ifdef CONFIG_IP_ROUTE_NAT if (rt->rt_flags & RTCF_NAT) ip_do_nat(skb); #endif skb->dev = dev; skb->protocol = __constant_htons(ETH_P_IP); /* * Multicasts are looped back for other local users */ if (rt->rt_flags&RTCF_MULTICAST && (!sk || sk->ip_mc_loop)) { #ifdef CONFIG_IP_MROUTE /* Small optimization: do not loopback not local frames, which returned after forwarding; they will be dropped by ip_mr_input in any case. Note, that local frames are looped back to be delivered to local recipients. This check is duplicated in ip_mr_input at the moment. */ if ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED)) #endif dev_loopback_xmit(skb); /* Multicasts with ttl 0 must not go beyond the host */ if (skb->nh.iph->ttl == 0) { kfree_skb(skb); return 0; } } if (rt->rt_flags&RTCF_BROADCAST) dev_loopback_xmit(skb); return ip_finish_output(skb); } int ip_output(struct sk_buff *skb) { #ifdef CONFIG_IP_ROUTE_NAT struct rtable *rt = (struct rtable*)skb->dst; #endif ip_statistics.IpOutRequests++; #ifdef CONFIG_IP_ROUTE_NAT if (rt->rt_flags&RTCF_NAT) ip_do_nat(skb); #endif return ip_finish_output(skb); } /* Queues a packet to be sent, and starts the transmitter if necessary. * This routine also needs to put in the total length and compute the * checksum. We use to do this in two stages, ip_build_header() then * this, but that scheme created a mess when routes disappeared etc. * So we do it all here, and the TCP send engine has been changed to * match. (No more unroutable FIN disasters, etc. wheee...) This will * most likely make other reliable transport layers above IP easier * to implement under Linux. */ void ip_queue_xmit(struct sk_buff *skb) { struct sock *sk = skb->sk; struct ip_options *opt = sk->opt; struct rtable *rt; struct device *dev; struct iphdr *iph; unsigned int tot_len; /* Make sure we can route this packet. */ rt = (struct rtable *) sk->dst_cache; if(rt == NULL || rt->u.dst.obsolete) { u32 daddr; sk->dst_cache = NULL; ip_rt_put(rt); /* Use correct destination address if we have options. */ daddr = sk->daddr; if(opt && opt->srr) daddr = opt->faddr; /* If this fails, retransmit mechanism of transport layer will * keep trying until route appears or the connection times itself * out. */ if(ip_route_output(&rt, daddr, sk->saddr, RT_TOS(sk->ip_tos) | RTO_CONN | sk->localroute, sk->bound_dev_if)) goto drop; sk->dst_cache = &rt->u.dst; } if(opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway) goto no_route; /* We have a route, so grab a reference. */ skb->dst = dst_clone(sk->dst_cache); /* OK, we know where to send it, allocate and build IP header. */ iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0)); iph->version = 4; iph->ihl = 5; iph->tos = sk->ip_tos; iph->frag_off = 0; iph->ttl = sk->ip_ttl; iph->daddr = rt->rt_dst; iph->saddr = rt->rt_src; iph->protocol = sk->protocol; skb->nh.iph = iph; /* Transport layer set skb->h.foo itself. */ if(opt && opt->optlen) { iph->ihl += opt->optlen >> 2; ip_options_build(skb, opt, sk->daddr, rt, 0); } tot_len = skb->len; iph->tot_len = htons(tot_len); iph->id = htons(ip_id_count++); dev = rt->u.dst.dev; #ifdef CONFIG_FIREWALL /* Now we have no better mechanism to notify about error. */ switch (call_out_firewall(PF_INET, dev, iph, NULL, &skb)) { case FW_REJECT: start_bh_atomic(); icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0); end_bh_atomic(); /* Fall thru... */ case FW_BLOCK: case FW_QUEUE: goto drop; } #endif /* This can happen when the transport layer has segments queued * with a cached route, and by the time we get here things are * re-routed to a device with a different MTU than the original * device. Sick, but we must cover it. */ if (skb_headroom(skb) < dev->hard_header_len && dev->hard_header) { struct sk_buff *skb2; skb2 = skb_realloc_headroom(skb, (dev->hard_header_len + 15) & ~15); kfree_skb(skb); if (skb2 == NULL) return; if (sk) skb_set_owner_w(skb2, sk); skb = skb2; iph = skb->nh.iph; } /* Do we need to fragment. Again this is inefficient. We * need to somehow lock the original buffer and use bits of it. */ if (tot_len > rt->u.dst.pmtu) goto fragment; if (ip_dont_fragment(sk, &rt->u.dst)) iph->frag_off |= __constant_htons(IP_DF); /* Add an IP checksum. */ ip_send_check(iph); skb->priority = sk->priority; skb->dst->output(skb); return; fragment: if (ip_dont_fragment(sk, &rt->u.dst) && tot_len > (iph->ihl<<2) + sizeof(struct tcphdr)+16) { /* Reject packet ONLY if TCP might fragment it itself, if were careful enough. Test is not precise (f.e. it does not take sacks into account). Actually, tcp should make it. --ANK (980801) */ iph->frag_off |= __constant_htons(IP_DF); NETDEBUG(printk(KERN_DEBUG "sending pkt_too_big to self\n")); /* icmp_send is not reenterable, so that bh_atomic... --ANK */ start_bh_atomic(); icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(rt->u.dst.pmtu)); end_bh_atomic(); goto drop; } ip_fragment(skb, skb->dst->output); return; no_route: sk->dst_cache = NULL; ip_rt_put(rt); ip_statistics.IpOutNoRoutes++; /* Fall through... */ drop: kfree_skb(skb); } /* * Build and send a packet, with as little as one copy * * Doesn't care much about ip options... option length can be * different for fragment at 0 and other fragments. * * Note that the fragment at the highest offset is sent first, * so the getfrag routine can fill in the TCP/UDP checksum header * field in the last fragment it sends... actually it also helps * the reassemblers, they can put most packets in at the head of * the fragment queue, and they know the total size in advance. This * last feature will measurably improve the Linux fragment handler one * day. * * The callback has five args, an arbitrary pointer (copy of frag), * the source IP address (may depend on the routing table), the * destination address (char *), the offset to copy from, and the * length to be copied. */ int ip_build_xmit_slow(struct sock *sk, int getfrag (const void *, char *, unsigned int, unsigned int), const void *frag, unsigned length, struct ipcm_cookie *ipc, struct rtable *rt, int flags) { unsigned int fraglen, maxfraglen, fragheaderlen; int err; int offset, mf; int mtu; unsigned short id; int hh_len = (rt->u.dst.dev->hard_header_len + 15)&~15; int nfrags=0; struct ip_options *opt = ipc->opt; int df = 0; mtu = rt->u.dst.pmtu; if (ip_dont_fragment(sk, &rt->u.dst)) df = htons(IP_DF); length -= sizeof(struct iphdr); if (opt) { fragheaderlen = sizeof(struct iphdr) + opt->optlen; maxfraglen = ((mtu-sizeof(struct iphdr)-opt->optlen) & ~7) + fragheaderlen; } else { fragheaderlen = sizeof(struct iphdr); /* * Fragheaderlen is the size of 'overhead' on each buffer. Now work * out the size of the frames to send. */ maxfraglen = ((mtu-sizeof(struct iphdr)) & ~7) + fragheaderlen; } if (length + fragheaderlen > 0xFFFF) { ip_local_error(sk, EMSGSIZE, rt->rt_dst, sk->dport, mtu); return -EMSGSIZE; } /* * Start at the end of the frame by handling the remainder. */ offset = length - (length % (maxfraglen - fragheaderlen)); /* * Amount of memory to allocate for final fragment. */ fraglen = length - offset + fragheaderlen; if (length-offset==0) { fraglen = maxfraglen; offset -= maxfraglen-fragheaderlen; } /* * The last fragment will not have MF (more fragments) set. */ mf = 0; /* * Don't fragment packets for path mtu discovery. */ if (offset > 0 && df) { ip_local_error(sk, EMSGSIZE, rt->rt_dst, sk->dport, mtu); return(-EMSGSIZE); } /* * Lock the device lists. */ dev_lock_list(); /* * Get an identifier */ id = htons(ip_id_count++); /* * Begin outputting the bytes. */ do { char *data; struct sk_buff * skb; /* * Get the memory we require with some space left for alignment. */ skb = sock_alloc_send_skb(sk, fraglen+hh_len+15, 0, flags&MSG_DONTWAIT, &err); if (skb == NULL) goto error; /* * Fill in the control structures */ skb->priority = sk->priority; skb->dst = dst_clone(&rt->u.dst); skb_reserve(skb, hh_len); /* * Find where to start putting bytes. */ data = skb_put(skb, fraglen); skb->nh.iph = (struct iphdr *)data; /* * Only write IP header onto non-raw packets */ { struct iphdr *iph = (struct iphdr *)data; iph->version = 4; iph->ihl = 5; if (opt) { iph->ihl += opt->optlen>>2; ip_options_build(skb, opt, ipc->addr, rt, offset); } iph->tos = sk->ip_tos; iph->tot_len = htons(fraglen - fragheaderlen + iph->ihl*4); iph->id = id; iph->frag_off = htons(offset>>3); iph->frag_off |= mf|df; if (rt->rt_type == RTN_MULTICAST) iph->ttl = sk->ip_mc_ttl; else iph->ttl = sk->ip_ttl; iph->protocol = sk->protocol; iph->check = 0; iph->saddr = rt->rt_src; iph->daddr = rt->rt_dst; iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl); data += iph->ihl*4; /* * Any further fragments will have MF set. */ mf = htons(IP_MF); } /* * User data callback */ if (getfrag(frag, data, offset, fraglen-fragheaderlen)) { err = -EFAULT; kfree_skb(skb); goto error; } offset -= (maxfraglen-fragheaderlen); fraglen = maxfraglen; nfrags++; #ifdef CONFIG_FIREWALL switch (call_out_firewall(PF_INET, rt->u.dst.dev, skb->nh.iph, NULL, &skb)) { case FW_QUEUE: kfree_skb(skb); continue; case FW_BLOCK: case FW_REJECT: kfree_skb(skb); err = -EPERM; goto error; } #endif err = -ENETDOWN; if (rt->u.dst.output(skb)) goto error; } while (offset >= 0); if (nfrags>1) ip_statistics.IpFragCreates += nfrags; dev_unlock_list(); return 0; error: ip_statistics.IpOutDiscards++; if (nfrags>1) ip_statistics.IpFragCreates += nfrags; dev_unlock_list(); return err; } /* * Fast path for unfragmented packets. */ int ip_build_xmit(struct sock *sk, int getfrag (const void *, char *, unsigned int, unsigned int), const void *frag, unsigned length, struct ipcm_cookie *ipc, struct rtable *rt, int flags) { int err; struct sk_buff *skb; int df; struct iphdr *iph; /* * Try the simple case first. This leaves fragmented frames, and by * choice RAW frames within 20 bytes of maximum size(rare) to the long path */ if (!sk->ip_hdrincl) { length += sizeof(struct iphdr); /* * Check for slow path. */ if (length > rt->u.dst.pmtu || ipc->opt != NULL) return ip_build_xmit_slow(sk,getfrag,frag,length,ipc,rt,flags); } else { if (length > rt->u.dst.dev->mtu) { ip_local_error(sk, EMSGSIZE, rt->rt_dst, sk->dport, rt->u.dst.dev->mtu); return -EMSGSIZE; } } /* * Do path mtu discovery if needed. */ df = 0; if (ip_dont_fragment(sk, &rt->u.dst)) df = htons(IP_DF); /* * Fast path for unfragmented frames without options. */ { int hh_len = (rt->u.dst.dev->hard_header_len + 15)&~15; skb = sock_alloc_send_skb(sk, length+hh_len+15, 0, flags&MSG_DONTWAIT, &err); if(skb==NULL) goto error; skb_reserve(skb, hh_len); } skb->priority = sk->priority; skb->dst = dst_clone(&rt->u.dst); skb->nh.iph = iph = (struct iphdr *)skb_put(skb, length); dev_lock_list(); if(!sk->ip_hdrincl) { iph->version=4; iph->ihl=5; iph->tos=sk->ip_tos; iph->tot_len = htons(length); iph->id=htons(ip_id_count++); iph->frag_off = df; iph->ttl=sk->ip_mc_ttl; if (rt->rt_type != RTN_MULTICAST) iph->ttl=sk->ip_ttl; iph->protocol=sk->protocol; iph->saddr=rt->rt_src; iph->daddr=rt->rt_dst; iph->check=0; iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl); err = getfrag(frag, ((char *)iph)+iph->ihl*4,0, length-iph->ihl*4); } else err = getfrag(frag, (void *)iph, 0, length); dev_unlock_list(); if (err) goto error_fault; #ifdef CONFIG_FIREWALL switch (call_out_firewall(PF_INET, rt->u.dst.dev, iph, NULL, &skb)) { case FW_QUEUE: kfree_skb(skb); return 0; case FW_BLOCK: case FW_REJECT: kfree_skb(skb); err = -EPERM; goto error; } #endif return rt->u.dst.output(skb); error_fault: err = -EFAULT; kfree_skb(skb); error: ip_statistics.IpOutDiscards++; return err; } /* * This IP datagram is too large to be sent in one piece. Break it up into * smaller pieces (each of size equal to IP header plus * a block of the data of the original IP data part) that will yet fit in a * single device frame, and queue such a frame for sending. * * Yes this is inefficient, feel free to submit a quicker one. */ void ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*)) { struct iphdr *iph; unsigned char *raw; unsigned char *ptr; struct device *dev; struct sk_buff *skb2; unsigned int mtu, hlen, left, len; int offset; int not_last_frag; struct rtable *rt = (struct rtable*)skb->dst; dev = rt->u.dst.dev; /* * Point into the IP datagram header. */ raw = skb->nh.raw; iph = (struct iphdr*)raw; /* * Setup starting values. */ hlen = iph->ihl * 4; left = ntohs(iph->tot_len) - hlen; /* Space per frame */ mtu = rt->u.dst.pmtu - hlen; /* Size of data space */ ptr = raw + hlen; /* Where to start from */ /* * The protocol doesn't seem to say what to do in the case that the * frame + options doesn't fit the mtu. As it used to fall down dead * in this case we were fortunate it didn't happen * * It is impossible, because mtu>=68. --ANK (980801) */ #ifdef CONFIG_NET_PARANOIA if (mtu<8) goto fail; #endif /* * Fragment the datagram. */ offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3; not_last_frag = iph->frag_off & htons(IP_MF); /* * Keep copying data until we run out. */ while(left > 0) { len = left; /* IF: it doesn't fit, use 'mtu' - the data space left */ if (len > mtu) len = mtu; /* IF: we are not sending upto and including the packet end then align the next start on an eight byte boundary */ if (len < left) { len &= ~7; } /* * Allocate buffer. */ if ((skb2 = alloc_skb(len+hlen+dev->hard_header_len+15,GFP_ATOMIC)) == NULL) { NETDEBUG(printk(KERN_INFO "IP: frag: no memory for new fragment!\n")); goto fail; } /* * Set up data on packet */ skb2->pkt_type = skb->pkt_type; skb2->priority = skb->priority; skb_reserve(skb2, (dev->hard_header_len+15)&~15); skb_put(skb2, len + hlen); skb2->nh.raw = skb2->data; skb2->h.raw = skb2->data + hlen; /* * Charge the memory for the fragment to any owner * it might possess */ if (skb->sk) skb_set_owner_w(skb2, skb->sk); skb2->dst = dst_clone(skb->dst); /* * Copy the packet header into the new buffer. */ memcpy(skb2->nh.raw, raw, hlen); /* * Copy a block of the IP datagram. */ memcpy(skb2->h.raw, ptr, len); left -= len; /* * Fill in the new header fields. */ iph = skb2->nh.iph; iph->frag_off = htons((offset >> 3)); /* ANK: dirty, but effective trick. Upgrade options only if * the segment to be fragmented was THE FIRST (otherwise, * options are already fixed) and make it ONCE * on the initial skb, so that all the following fragments * will inherit fixed options. */ if (offset == 0) ip_options_fragment(skb); /* * Added AC : If we are fragmenting a fragment that's not the * last fragment then keep MF on each bit */ if (left > 0 || not_last_frag) iph->frag_off |= htons(IP_MF); ptr += len; offset += len; /* * Put this fragment into the sending queue. */ ip_statistics.IpFragCreates++; iph->tot_len = htons(len + hlen); ip_send_check(iph); output(skb2); } kfree_skb(skb); ip_statistics.IpFragOKs++; return; fail: kfree_skb(skb); ip_statistics.IpFragFails++; } /* * Fetch data from kernel space and fill in checksum if needed. */ static int ip_reply_glue_bits(const void *dptr, char *to, unsigned int offset, unsigned int fraglen) { struct ip_reply_arg *dp = (struct ip_reply_arg*)dptr; u16 *pktp = (u16 *)to; struct iovec *iov; int len; int hdrflag = 1; iov = &dp->iov[0]; if (offset >= iov->iov_len) { offset -= iov->iov_len; iov++; hdrflag = 0; } len = iov->iov_len - offset; if (fraglen > len) { /* overlapping. */ dp->csum = csum_partial_copy_nocheck(iov->iov_base+offset, to, len, dp->csum); offset = 0; fraglen -= len; to += len; iov++; } dp->csum = csum_partial_copy_nocheck(iov->iov_base+offset, to, fraglen, dp->csum); if (hdrflag && dp->csumoffset) *(pktp + dp->csumoffset) = csum_fold(dp->csum); /* fill in checksum */ return 0; } /* * Generic function to send a packet as reply to another packet. * Used to send TCP resets so far. ICMP should use this function too. * * Should run single threaded per socket because it uses the sock * structure to pass arguments. */ void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg, unsigned int len) { struct { struct ip_options opt; char data[40]; } replyopts; struct ipcm_cookie ipc; u32 daddr; struct rtable *rt = (struct rtable*)skb->dst; if (ip_options_echo(&replyopts.opt, skb)) return; sk->ip_tos = skb->nh.iph->tos; sk->priority = skb->priority; sk->protocol = skb->nh.iph->protocol; daddr = ipc.addr = rt->rt_src; ipc.opt = &replyopts.opt; if (ipc.opt->srr) daddr = replyopts.opt.faddr; if (ip_route_output(&rt, daddr, rt->rt_spec_dst, RT_TOS(skb->nh.iph->tos), 0)) return; /* And let IP do all the hard work. */ ip_build_xmit(sk, ip_reply_glue_bits, arg, len, &ipc, rt, MSG_DONTWAIT); ip_rt_put(rt); } /* * IP protocol layer initialiser */ static struct packet_type ip_packet_type = { __constant_htons(ETH_P_IP), NULL, /* All devices */ ip_rcv, NULL, NULL, }; #ifdef CONFIG_PROC_FS #ifdef CONFIG_IP_MULTICAST static struct proc_dir_entry proc_net_igmp = { PROC_NET_IGMP, 4, "igmp", S_IFREG | S_IRUGO, 1, 0, 0, 0, &proc_net_inode_operations, ip_mc_procinfo }; #endif #endif /* * IP registers the packet type and then calls the subprotocol initialisers */ __initfunc(void ip_init(void)) { dev_add_pack(&ip_packet_type); ip_rt_init(); #ifdef CONFIG_PROC_FS #ifdef CONFIG_IP_MULTICAST proc_net_register(&proc_net_igmp); #endif #endif }