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ip_output.c
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/*
* 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 1.100 2002/02/01 22:01:03 davem Exp $
*
* Authors: Ross Biro
* Fred N. van Kempen, <[email protected]>
* Donald Becker, <[email protected]>
* Alan Cox, <[email protected]>
* Richard Underwood
* Stefan Becker, <[email protected]>
* Jorge Cwik, <[email protected]>
* Arnt Gulbrandsen, <[email protected]>
* Hirokazu Takahashi, <[email protected]>
*
* 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.
* Detlev Wengorz : Copy protocol for fragments.
* Hirokazu Takahashi: HW checksumming for outgoing UDP
* datagrams.
* Hirokazu Takahashi: sendfile() on UDP works now.
*/
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/highmem.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/xfrm.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/arp.h>
#include <net/icmp.h>
#include <net/checksum.h>
#include <net/inetpeer.h>
#include <linux/igmp.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_bridge.h>
#include <linux/mroute.h>
#include <linux/netlink.h>
#include <linux/tcp.h>
int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
/* 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);
}
int __ip_local_out(struct sk_buff *skb)
{
struct iphdr *iph = ip_hdr(skb);
iph->tot_len = htons(skb->len);
ip_send_check(iph);
return nf_hook(PF_INET, NF_INET_LOCAL_OUT, skb, NULL, skb->dst->dev,
dst_output);
}
int ip_local_out(struct sk_buff *skb)
{
int err;
err = __ip_local_out(skb);
if (likely(err == 1))
err = dst_output(skb);
return err;
}
EXPORT_SYMBOL_GPL(ip_local_out);
/* dev_loopback_xmit for use with netfilter. */
static int ip_dev_loopback_xmit(struct sk_buff *newskb)
{
skb_reset_mac_header(newskb);
__skb_pull(newskb, skb_network_offset(newskb));
newskb->pkt_type = PACKET_LOOPBACK;
newskb->ip_summed = CHECKSUM_UNNECESSARY;
BUG_TRAP(newskb->dst);
netif_rx(newskb);
return 0;
}
static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
{
int ttl = inet->uc_ttl;
if (ttl < 0)
ttl = dst_metric(dst, RTAX_HOPLIMIT);
return ttl;
}
/*
* Add an ip header to a skbuff and send it out.
*
*/
int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
__be32 saddr, __be32 daddr, struct ip_options *opt)
{
struct inet_sock *inet = inet_sk(sk);
struct rtable *rt = skb->rtable;
struct iphdr *iph;
/* Build the IP header. */
skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
skb_reset_network_header(skb);
iph = ip_hdr(skb);
iph->version = 4;
iph->ihl = 5;
iph->tos = inet->tos;
if (ip_dont_fragment(sk, &rt->u.dst))
iph->frag_off = htons(IP_DF);
else
iph->frag_off = 0;
iph->ttl = ip_select_ttl(inet, &rt->u.dst);
iph->daddr = rt->rt_dst;
iph->saddr = rt->rt_src;
iph->protocol = sk->sk_protocol;
ip_select_ident(iph, &rt->u.dst, sk);
if (opt && opt->optlen) {
iph->ihl += opt->optlen>>2;
ip_options_build(skb, opt, daddr, rt, 0);
}
skb->priority = sk->sk_priority;
skb->mark = sk->sk_mark;
/* Send it out. */
return ip_local_out(skb);
}
EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
static inline int ip_finish_output2(struct sk_buff *skb)
{
struct dst_entry *dst = skb->dst;
struct rtable *rt = (struct rtable *)dst;
struct net_device *dev = dst->dev;
unsigned int hh_len = LL_RESERVED_SPACE(dev);
if (rt->rt_type == RTN_MULTICAST)
IP_INC_STATS(IPSTATS_MIB_OUTMCASTPKTS);
else if (rt->rt_type == RTN_BROADCAST)
IP_INC_STATS(IPSTATS_MIB_OUTBCASTPKTS);
/* Be paranoid, rather than too clever. */
if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
struct sk_buff *skb2;
skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
if (skb2 == NULL) {
kfree_skb(skb);
return -ENOMEM;
}
if (skb->sk)
skb_set_owner_w(skb2, skb->sk);
kfree_skb(skb);
skb = skb2;
}
if (dst->hh)
return neigh_hh_output(dst->hh, skb);
else if (dst->neighbour)
return dst->neighbour->output(skb);
if (net_ratelimit())
printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
kfree_skb(skb);
return -EINVAL;
}
static inline int ip_skb_dst_mtu(struct sk_buff *skb)
{
struct inet_sock *inet = skb->sk ? inet_sk(skb->sk) : NULL;
return (inet && inet->pmtudisc == IP_PMTUDISC_PROBE) ?
skb->dst->dev->mtu : dst_mtu(skb->dst);
}
static int ip_finish_output(struct sk_buff *skb)
{
#if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
/* Policy lookup after SNAT yielded a new policy */
if (skb->dst->xfrm != NULL) {
IPCB(skb)->flags |= IPSKB_REROUTED;
return dst_output(skb);
}
#endif
if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
return ip_fragment(skb, ip_finish_output2);
else
return ip_finish_output2(skb);
}
int ip_mc_output(struct sk_buff *skb)
{
struct sock *sk = skb->sk;
struct rtable *rt = skb->rtable;
struct net_device *dev = rt->u.dst.dev;
/*
* If the indicated interface is up and running, send the packet.
*/
IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
skb->dev = dev;
skb->protocol = htons(ETH_P_IP);
/*
* Multicasts are looped back for other local users
*/
if (rt->rt_flags&RTCF_MULTICAST) {
if ((!sk || inet_sk(sk)->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.
*/
&& ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
#endif
) {
struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
if (newskb)
NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb,
NULL, newskb->dev,
ip_dev_loopback_xmit);
}
/* Multicasts with ttl 0 must not go beyond the host */
if (ip_hdr(skb)->ttl == 0) {
kfree_skb(skb);
return 0;
}
}
if (rt->rt_flags&RTCF_BROADCAST) {
struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
if (newskb)
NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb, NULL,
newskb->dev, ip_dev_loopback_xmit);
}
return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, skb->dev,
ip_finish_output,
!(IPCB(skb)->flags & IPSKB_REROUTED));
}
int ip_output(struct sk_buff *skb)
{
struct net_device *dev = skb->dst->dev;
IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
skb->dev = dev;
skb->protocol = htons(ETH_P_IP);
return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, dev,
ip_finish_output,
!(IPCB(skb)->flags & IPSKB_REROUTED));
}
int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
{
struct sock *sk = skb->sk;
struct inet_sock *inet = inet_sk(sk);
struct ip_options *opt = inet->opt;
struct rtable *rt;
struct iphdr *iph;
/* Skip all of this if the packet is already routed,
* f.e. by something like SCTP.
*/
rt = skb->rtable;
if (rt != NULL)
goto packet_routed;
/* Make sure we can route this packet. */
rt = (struct rtable *)__sk_dst_check(sk, 0);
if (rt == NULL) {
__be32 daddr;
/* Use correct destination address if we have options. */
daddr = inet->daddr;
if(opt && opt->srr)
daddr = opt->faddr;
{
struct flowi fl = { .oif = sk->sk_bound_dev_if,
.nl_u = { .ip4_u =
{ .daddr = daddr,
.saddr = inet->saddr,
.tos = RT_CONN_FLAGS(sk) } },
.proto = sk->sk_protocol,
.uli_u = { .ports =
{ .sport = inet->sport,
.dport = inet->dport } } };
/* If this fails, retransmit mechanism of transport layer will
* keep trying until route appears or the connection times
* itself out.
*/
security_sk_classify_flow(sk, &fl);
if (ip_route_output_flow(sock_net(sk), &rt, &fl, sk, 0))
goto no_route;
}
sk_setup_caps(sk, &rt->u.dst);
}
skb->dst = dst_clone(&rt->u.dst);
packet_routed:
if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
goto no_route;
/* OK, we know where to send it, allocate and build IP header. */
skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
skb_reset_network_header(skb);
iph = ip_hdr(skb);
*((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
iph->frag_off = htons(IP_DF);
else
iph->frag_off = 0;
iph->ttl = ip_select_ttl(inet, &rt->u.dst);
iph->protocol = sk->sk_protocol;
iph->saddr = rt->rt_src;
iph->daddr = rt->rt_dst;
/* Transport layer set skb->h.foo itself. */
if (opt && opt->optlen) {
iph->ihl += opt->optlen >> 2;
ip_options_build(skb, opt, inet->daddr, rt, 0);
}
ip_select_ident_more(iph, &rt->u.dst, sk,
(skb_shinfo(skb)->gso_segs ?: 1) - 1);
skb->priority = sk->sk_priority;
skb->mark = sk->sk_mark;
return ip_local_out(skb);
no_route:
IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES);
kfree_skb(skb);
return -EHOSTUNREACH;
}
static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
{
to->pkt_type = from->pkt_type;
to->priority = from->priority;
to->protocol = from->protocol;
dst_release(to->dst);
to->dst = dst_clone(from->dst);
to->dev = from->dev;
to->mark = from->mark;
/* Copy the flags to each fragment. */
IPCB(to)->flags = IPCB(from)->flags;
#ifdef CONFIG_NET_SCHED
to->tc_index = from->tc_index;
#endif
nf_copy(to, from);
#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
to->nf_trace = from->nf_trace;
#endif
#if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
to->ipvs_property = from->ipvs_property;
#endif
skb_copy_secmark(to, from);
}
/*
* 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.
*/
int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
{
struct iphdr *iph;
int raw = 0;
int ptr;
struct net_device *dev;
struct sk_buff *skb2;
unsigned int mtu, hlen, left, len, ll_rs, pad;
int offset;
__be16 not_last_frag;
struct rtable *rt = skb->rtable;
int err = 0;
dev = rt->u.dst.dev;
/*
* Point into the IP datagram header.
*/
iph = ip_hdr(skb);
if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
htonl(ip_skb_dst_mtu(skb)));
kfree_skb(skb);
return -EMSGSIZE;
}
/*
* Setup starting values.
*/
hlen = iph->ihl * 4;
mtu = dst_mtu(&rt->u.dst) - hlen; /* Size of data space */
IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
/* When frag_list is given, use it. First, check its validity:
* some transformers could create wrong frag_list or break existing
* one, it is not prohibited. In this case fall back to copying.
*
* LATER: this step can be merged to real generation of fragments,
* we can switch to copy when see the first bad fragment.
*/
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *frag;
int first_len = skb_pagelen(skb);
int truesizes = 0;
if (first_len - hlen > mtu ||
((first_len - hlen) & 7) ||
(iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
skb_cloned(skb))
goto slow_path;
for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {
/* Correct geometry. */
if (frag->len > mtu ||
((frag->len & 7) && frag->next) ||
skb_headroom(frag) < hlen)
goto slow_path;
/* Partially cloned skb? */
if (skb_shared(frag))
goto slow_path;
BUG_ON(frag->sk);
if (skb->sk) {
sock_hold(skb->sk);
frag->sk = skb->sk;
frag->destructor = sock_wfree;
truesizes += frag->truesize;
}
}
/* Everything is OK. Generate! */
err = 0;
offset = 0;
frag = skb_shinfo(skb)->frag_list;
skb_shinfo(skb)->frag_list = NULL;
skb->data_len = first_len - skb_headlen(skb);
skb->truesize -= truesizes;
skb->len = first_len;
iph->tot_len = htons(first_len);
iph->frag_off = htons(IP_MF);
ip_send_check(iph);
for (;;) {
/* Prepare header of the next frame,
* before previous one went down. */
if (frag) {
frag->ip_summed = CHECKSUM_NONE;
skb_reset_transport_header(frag);
__skb_push(frag, hlen);
skb_reset_network_header(frag);
memcpy(skb_network_header(frag), iph, hlen);
iph = ip_hdr(frag);
iph->tot_len = htons(frag->len);
ip_copy_metadata(frag, skb);
if (offset == 0)
ip_options_fragment(frag);
offset += skb->len - hlen;
iph->frag_off = htons(offset>>3);
if (frag->next != NULL)
iph->frag_off |= htons(IP_MF);
/* Ready, complete checksum */
ip_send_check(iph);
}
err = output(skb);
if (!err)
IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
if (err || !frag)
break;
skb = frag;
frag = skb->next;
skb->next = NULL;
}
if (err == 0) {
IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
return 0;
}
while (frag) {
skb = frag->next;
kfree_skb(frag);
frag = skb;
}
IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
return err;
}
slow_path:
left = skb->len - hlen; /* Space per frame */
ptr = raw + hlen; /* Where to start from */
/* for bridged IP traffic encapsulated inside f.e. a vlan header,
* we need to make room for the encapsulating header
*/
pad = nf_bridge_pad(skb);
ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, pad);
mtu -= pad;
/*
* 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+ll_rs, GFP_ATOMIC)) == NULL) {
NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
err = -ENOMEM;
goto fail;
}
/*
* Set up data on packet
*/
ip_copy_metadata(skb2, skb);
skb_reserve(skb2, ll_rs);
skb_put(skb2, len + hlen);
skb_reset_network_header(skb2);
skb2->transport_header = skb2->network_header + hlen;
/*
* Charge the memory for the fragment to any owner
* it might possess
*/
if (skb->sk)
skb_set_owner_w(skb2, skb->sk);
/*
* Copy the packet header into the new buffer.
*/
skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
/*
* Copy a block of the IP datagram.
*/
if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
BUG();
left -= len;
/*
* Fill in the new header fields.
*/
iph = ip_hdr(skb2);
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.
*/
iph->tot_len = htons(len + hlen);
ip_send_check(iph);
err = output(skb2);
if (err)
goto fail;
IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
}
kfree_skb(skb);
IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
return err;
fail:
kfree_skb(skb);
IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
return err;
}
EXPORT_SYMBOL(ip_fragment);
int
ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
{
struct iovec *iov = from;
if (skb->ip_summed == CHECKSUM_PARTIAL) {
if (memcpy_fromiovecend(to, iov, offset, len) < 0)
return -EFAULT;
} else {
__wsum csum = 0;
if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
return -EFAULT;
skb->csum = csum_block_add(skb->csum, csum, odd);
}
return 0;
}
static inline __wsum
csum_page(struct page *page, int offset, int copy)
{
char *kaddr;
__wsum csum;
kaddr = kmap(page);
csum = csum_partial(kaddr + offset, copy, 0);
kunmap(page);
return csum;
}
static inline int ip_ufo_append_data(struct sock *sk,
int getfrag(void *from, char *to, int offset, int len,
int odd, struct sk_buff *skb),
void *from, int length, int hh_len, int fragheaderlen,
int transhdrlen, int mtu,unsigned int flags)
{
struct sk_buff *skb;
int err;
/* There is support for UDP fragmentation offload by network
* device, so create one single skb packet containing complete
* udp datagram
*/
if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
skb = sock_alloc_send_skb(sk,
hh_len + fragheaderlen + transhdrlen + 20,
(flags & MSG_DONTWAIT), &err);
if (skb == NULL)
return err;
/* reserve space for Hardware header */
skb_reserve(skb, hh_len);
/* create space for UDP/IP header */
skb_put(skb,fragheaderlen + transhdrlen);
/* initialize network header pointer */
skb_reset_network_header(skb);
/* initialize protocol header pointer */
skb->transport_header = skb->network_header + fragheaderlen;
skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum = 0;
sk->sk_sndmsg_off = 0;
/* specify the length of each IP datagram fragment */
skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
__skb_queue_tail(&sk->sk_write_queue, skb);
}
return skb_append_datato_frags(sk, skb, getfrag, from,
(length - transhdrlen));
}
/*
* ip_append_data() and ip_append_page() can make one large IP datagram
* from many pieces of data. Each pieces will be holded on the socket
* until ip_push_pending_frames() is called. Each piece can be a page
* or non-page data.
*
* Not only UDP, other transport protocols - e.g. raw sockets - can use
* this interface potentially.
*
* LATER: length must be adjusted by pad at tail, when it is required.
*/
int ip_append_data(struct sock *sk,
int getfrag(void *from, char *to, int offset, int len,
int odd, struct sk_buff *skb),
void *from, int length, int transhdrlen,
struct ipcm_cookie *ipc, struct rtable *rt,
unsigned int flags)
{
struct inet_sock *inet = inet_sk(sk);
struct sk_buff *skb;
struct ip_options *opt = NULL;
int hh_len;
int exthdrlen;
int mtu;
int copy;
int err;
int offset = 0;
unsigned int maxfraglen, fragheaderlen;
int csummode = CHECKSUM_NONE;
if (flags&MSG_PROBE)
return 0;
if (skb_queue_empty(&sk->sk_write_queue)) {
/*
* setup for corking.
*/
opt = ipc->opt;
if (opt) {
if (inet->cork.opt == NULL) {
inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
if (unlikely(inet->cork.opt == NULL))
return -ENOBUFS;
}
memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
inet->cork.flags |= IPCORK_OPT;
inet->cork.addr = ipc->addr;
}
dst_hold(&rt->u.dst);
inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
rt->u.dst.dev->mtu :
dst_mtu(rt->u.dst.path);
inet->cork.dst = &rt->u.dst;
inet->cork.length = 0;
sk->sk_sndmsg_page = NULL;
sk->sk_sndmsg_off = 0;
if ((exthdrlen = rt->u.dst.header_len) != 0) {
length += exthdrlen;
transhdrlen += exthdrlen;
}
} else {
rt = (struct rtable *)inet->cork.dst;
if (inet->cork.flags & IPCORK_OPT)
opt = inet->cork.opt;
transhdrlen = 0;
exthdrlen = 0;
mtu = inet->cork.fragsize;
}
hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
return -EMSGSIZE;
}
/*
* transhdrlen > 0 means that this is the first fragment and we wish
* it won't be fragmented in the future.
*/
if (transhdrlen &&
length + fragheaderlen <= mtu &&
rt->u.dst.dev->features & NETIF_F_V4_CSUM &&
!exthdrlen)
csummode = CHECKSUM_PARTIAL;
inet->cork.length += length;
if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
(sk->sk_protocol == IPPROTO_UDP) &&
(rt->u.dst.dev->features & NETIF_F_UFO)) {
err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
fragheaderlen, transhdrlen, mtu,
flags);
if (err)
goto error;
return 0;
}
/* So, what's going on in the loop below?
*
* We use calculated fragment length to generate chained skb,
* each of segments is IP fragment ready for sending to network after
* adding appropriate IP header.
*/
if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
goto alloc_new_skb;
while (length > 0) {
/* Check if the remaining data fits into current packet. */
copy = mtu - skb->len;
if (copy < length)
copy = maxfraglen - skb->len;
if (copy <= 0) {
char *data;
unsigned int datalen;
unsigned int fraglen;
unsigned int fraggap;
unsigned int alloclen;
struct sk_buff *skb_prev;
alloc_new_skb:
skb_prev = skb;
if (skb_prev)
fraggap = skb_prev->len - maxfraglen;
else
fraggap = 0;
/*
* If remaining data exceeds the mtu,
* we know we need more fragment(s).
*/
datalen = length + fraggap;
if (datalen > mtu - fragheaderlen)
datalen = maxfraglen - fragheaderlen;
fraglen = datalen + fragheaderlen;
if ((flags & MSG_MORE) &&
!(rt->u.dst.dev->features&NETIF_F_SG))
alloclen = mtu;
else
alloclen = datalen + fragheaderlen;
/* The last fragment gets additional space at tail.
* Note, with MSG_MORE we overallocate on fragments,
* because we have no idea what fragment will be
* the last.
*/
if (datalen == length + fraggap)
alloclen += rt->u.dst.trailer_len;
if (transhdrlen) {
skb = sock_alloc_send_skb(sk,
alloclen + hh_len + 15,
(flags & MSG_DONTWAIT), &err);
} else {
skb = NULL;
if (atomic_read(&sk->sk_wmem_alloc) <=
2 * sk->sk_sndbuf)
skb = sock_wmalloc(sk,
alloclen + hh_len + 15, 1,
sk->sk_allocation);
if (unlikely(skb == NULL))
err = -ENOBUFS;
}
if (skb == NULL)
goto error;
/*
* Fill in the control structures
*/
skb->ip_summed = csummode;
skb->csum = 0;
skb_reserve(skb, hh_len);
/*
* Find where to start putting bytes.
*/
data = skb_put(skb, fraglen);
skb_set_network_header(skb, exthdrlen);
skb->transport_header = (skb->network_header +
fragheaderlen);
data += fragheaderlen;
if (fraggap) {
skb->csum = skb_copy_and_csum_bits(
skb_prev, maxfraglen,
data + transhdrlen, fraggap, 0);
skb_prev->csum = csum_sub(skb_prev->csum,
skb->csum);
data += fraggap;
pskb_trim_unique(skb_prev, maxfraglen);
}
copy = datalen - transhdrlen - fraggap;
if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
err = -EFAULT;
kfree_skb(skb);
goto error;
}
offset += copy;
length -= datalen - fraggap;
transhdrlen = 0;
exthdrlen = 0;
csummode = CHECKSUM_NONE;
/*
* Put the packet on the pending queue.
*/
__skb_queue_tail(&sk->sk_write_queue, skb);
continue;
}
if (copy > length)
copy = length;
if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
unsigned int off;
off = skb->len;
if (getfrag(from, skb_put(skb, copy),
offset, copy, off, skb) < 0) {
__skb_trim(skb, off);
err = -EFAULT;
goto error;
}
} else {
int i = skb_shinfo(skb)->nr_frags;
skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
struct page *page = sk->sk_sndmsg_page;