cregit-Linux how code gets into the kernel

Release 4.14 net/ipv6/ip6_output.c

Directory: net/ipv6
 *      IPv6 output functions
 *      Linux INET6 implementation
 *      Authors:
 *      Pedro Roque             <>
 *      Based on linux/net/ipv4/ip_output.c
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *      Changes:
 *      A.N.Kuznetsov   :       airthmetics in fragmentation.
 *                              extension headers are implemented.
 *                              route changes now work.
 *                              ip6_forward does not confuse sniffers.
 *                              etc.
 *      H. von Brand    :       Added missing #include <linux/string.h>
 *      Imran Patel     :       frag id should be in NBO
 *      Kazunori MIYAZAWA @USAGI
 *                      :       add ip6_append_data and related functions
 *                              for datagram xmit

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/in6.h>
#include <linux/tcp.h>
#include <linux/route.h>
#include <linux/module.h>
#include <linux/slab.h>

#include <linux/bpf-cgroup.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>

#include <net/sock.h>
#include <net/snmp.h>

#include <net/ipv6.h>
#include <net/ndisc.h>
#include <net/protocol.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/rawv6.h>
#include <net/icmp.h>
#include <net/xfrm.h>
#include <net/checksum.h>
#include <linux/mroute6.h>
#include <net/l3mdev.h>
#include <net/lwtunnel.h>

static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb) { struct dst_entry *dst = skb_dst(skb); struct net_device *dev = dst->dev; struct neighbour *neigh; struct in6_addr *nexthop; int ret; if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) { struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb)); if (!(dev->flags & IFF_LOOPBACK) && sk_mc_loop(sk) && ((mroute6_socket(net, skb) && !(IP6CB(skb)->flags & IP6SKB_FORWARDED)) || ipv6_chk_mcast_addr(dev, &ipv6_hdr(skb)->daddr, &ipv6_hdr(skb)->saddr))) { struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC); /* Do not check for IFF_ALLMULTI; multicast routing is not supported in any case. */ if (newskb) NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, sk, newskb, NULL, newskb->dev, dev_loopback_xmit); if (ipv6_hdr(skb)->hop_limit == 0) { IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS); kfree_skb(skb); return 0; } } IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUTMCAST, skb->len); if (IPV6_ADDR_MC_SCOPE(&ipv6_hdr(skb)->daddr) <= IPV6_ADDR_SCOPE_NODELOCAL && !(dev->flags & IFF_LOOPBACK)) { kfree_skb(skb); return 0; } } if (lwtunnel_xmit_redirect(dst->lwtstate)) { int res = lwtunnel_xmit(skb); if (res < 0 || res == LWTUNNEL_XMIT_DONE) return res; } rcu_read_lock_bh(); nexthop = rt6_nexthop((struct rt6_info *)dst, &ipv6_hdr(skb)->daddr); neigh = __ipv6_neigh_lookup_noref(dst->dev, nexthop); if (unlikely(!neigh)) neigh = __neigh_create(&nd_tbl, nexthop, dst->dev, false); if (!IS_ERR(neigh)) { sock_confirm_neigh(skb, neigh); ret = neigh_output(neigh, skb); rcu_read_unlock_bh(); return ret; } rcu_read_unlock_bh(); IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES); kfree_skb(skb); return -EINVAL; }


Linus Torvalds (pre-git)11728.96%615.00%
Hideaki Yoshifuji / 吉藤英明9222.77%410.00%
Hannes Frederic Sowa358.66%25.00%
David S. Miller327.92%615.00%
Roopa Prabhu327.92%12.50%
Jan Engelhardt225.45%25.00%
Arnaldo Carvalho de Melo122.97%12.50%
Eric W. Biedermann112.72%37.50%
Julian Anastasov81.98%25.00%
Martin KaFai Lau81.98%12.50%
Neil Horman61.49%12.50%
Eric Dumazet61.49%12.50%
David L Stevens51.24%12.50%
Shirley Ma51.24%25.00%
Octavian Purdila40.99%12.50%
Patrick McHardy30.74%25.00%
Denis V. Lunev20.50%12.50%
Benjamin Thery20.50%12.50%
Herbert Xu10.25%12.50%
Michel Machado10.25%12.50%

static int ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb) { int ret; ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb); if (ret) { kfree_skb(skb); return ret; } if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) || dst_allfrag(skb_dst(skb)) || (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size)) return ip6_fragment(net, sk, skb, ip6_finish_output2); else return ip6_finish_output2(net, sk, skb); }


Jan Engelhardt5345.30%116.67%
Daniel Mack2622.22%116.67%
Jiri Pirko2017.09%116.67%
David S. Miller97.69%116.67%
Eric W. Biedermann97.69%233.33%

int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb) { struct net_device *dev = skb_dst(skb)->dev; struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb)); skb->protocol = htons(ETH_P_IPV6); skb->dev = dev; if (unlikely(idev->cnf.disable_ipv6)) { IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS); kfree_skb(skb); return 0; } return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, sk, skb, NULL, dev, ip6_finish_output, !(IP6CB(skb)->flags & IP6SKB_REROUTED)); }


Hideaki Yoshifuji / 吉藤英明3831.15%17.69%
Jan Engelhardt3427.87%215.38%
Chenbo Feng1512.30%17.69%
Kazunori Miyazawa1411.48%17.69%
Eric Dumazet86.56%215.38%
Eric W. Biedermann86.56%323.08%
David S. Miller21.64%17.69%
Herbert Xu21.64%17.69%
Denis V. Lunev10.82%17.69%

/* * xmit an sk_buff (used by TCP, SCTP and DCCP) * Note : socket lock is not held for SYNACK packets, but might be modified * by calls to skb_set_owner_w() and ipv6_local_error(), * which are using proper atomic operations or spinlocks. */
int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, __u32 mark, struct ipv6_txoptions *opt, int tclass) { struct net *net = sock_net(sk); const struct ipv6_pinfo *np = inet6_sk(sk); struct in6_addr *first_hop = &fl6->daddr; struct dst_entry *dst = skb_dst(skb); struct ipv6hdr *hdr; u8 proto = fl6->flowi6_proto; int seg_len = skb->len; int hlimit = -1; u32 mtu; if (opt) { unsigned int head_room; /* First: exthdrs may take lots of space (~8K for now) MAX_HEADER is not enough. */ head_room = opt->opt_nflen + opt->opt_flen; seg_len += head_room; head_room += sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dst->dev); if (skb_headroom(skb) < head_room) { struct sk_buff *skb2 = skb_realloc_headroom(skb, head_room); if (!skb2) { IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_OUTDISCARDS); kfree_skb(skb); return -ENOBUFS; } consume_skb(skb); skb = skb2; /* skb_set_owner_w() changes sk->sk_wmem_alloc atomically, * it is safe to call in our context (socket lock not held) */ skb_set_owner_w(skb, (struct sock *)sk); } if (opt->opt_flen) ipv6_push_frag_opts(skb, opt, &proto); if (opt->opt_nflen) ipv6_push_nfrag_opts(skb, opt, &proto, &first_hop, &fl6->saddr); } skb_push(skb, sizeof(struct ipv6hdr)); skb_reset_network_header(skb); hdr = ipv6_hdr(skb); /* * Fill in the IPv6 header */ if (np) hlimit = np->hop_limit; if (hlimit < 0) hlimit = ip6_dst_hoplimit(dst); ip6_flow_hdr(hdr, tclass, ip6_make_flowlabel(net, skb, fl6->flowlabel, np->autoflowlabel, fl6)); hdr->payload_len = htons(seg_len); hdr->nexthdr = proto; hdr->hop_limit = hlimit; hdr->saddr = fl6->saddr; hdr->daddr = *first_hop; skb->protocol = htons(ETH_P_IPV6); skb->priority = sk->sk_priority; skb->mark = mark; mtu = dst_mtu(dst); if ((skb->len <= mtu) || skb->ignore_df || skb_is_gso(skb)) { IP6_UPD_PO_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_OUT, skb->len); /* if egress device is enslaved to an L3 master device pass the * skb to its handler for processing */ skb = l3mdev_ip6_out((struct sock *)sk, skb); if (unlikely(!skb)) return 0; /* hooks should never assume socket lock is held. * we promote our socket to non const */ return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, (struct sock *)sk, skb, NULL, dst->dev, dst_output); } skb->dev = dst->dev; /* ipv6_local_error() does not require socket lock, * we promote our socket to non const */ ipv6_local_error((struct sock *)sk, EMSGSIZE, fl6, mtu); IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_FRAGFAILS); kfree_skb(skb); return -EMSGSIZE; }


Linus Torvalds (pre-git)27350.84%916.36%
Hideaki Yoshifuji / 吉藤英明468.57%712.73%
Eric Dumazet366.70%47.27%
David Ahern264.84%11.82%
David S. Miller173.17%59.09%
Denis V. Lunev162.98%11.82%
Tom Herbert132.42%23.64%
Arnaldo Carvalho de Melo122.23%23.64%
Alexey Kuznetsov112.05%11.82%
Sridhar Samudrala112.05%11.82%
Shirley Ma101.86%11.82%
Hannes Frederic Sowa91.68%11.82%
Patrick McHardy91.68%23.64%
Neil Horman61.12%11.82%
Herbert Xu61.12%35.45%
David Lebrun50.93%11.82%
Tóth László Attila50.93%11.82%
Gerrit Renker40.74%11.82%
Pablo Neira Ayuso40.74%11.82%
Steffen Klassert40.74%11.82%
Alexey Dobriyan30.56%11.82%
Eric W. Biedermann30.56%23.64%
Kazunori Miyazawa20.37%11.82%
Wei Yongjun20.37%11.82%
Ian Morris10.19%11.82%
Chuck Lever10.19%11.82%
Américo Wang10.19%11.82%
Jan Engelhardt10.19%11.82%

static int ip6_call_ra_chain(struct sk_buff *skb, int sel) { struct ip6_ra_chain *ra; struct sock *last = NULL; read_lock(&ip6_ra_lock); for (ra = ip6_ra_chain; ra; ra = ra->next) { struct sock *sk = ra->sk; if (sk && ra->sel == sel && (!sk->sk_bound_dev_if || sk->sk_bound_dev_if == skb->dev->ifindex)) { if (last) { struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); if (skb2) rawv6_rcv(last, skb2); } last = sk; } } if (last) { rawv6_rcv(last, skb); read_unlock(&ip6_ra_lock); return 1; } read_unlock(&ip6_ra_lock); return 0; }


Linus Torvalds (pre-git)13288.00%360.00%
Andrew McDonald1711.33%120.00%
Adrian Bunk10.67%120.00%

static int ip6_forward_proxy_check(struct sk_buff *skb) { struct ipv6hdr *hdr = ipv6_hdr(skb); u8 nexthdr = hdr->nexthdr; __be16 frag_off; int offset; if (ipv6_ext_hdr(nexthdr)) { offset = ipv6_skip_exthdr(skb, sizeof(*hdr), &nexthdr, &frag_off); if (offset < 0) return 0; } else offset = sizeof(struct ipv6hdr); if (nexthdr == IPPROTO_ICMPV6) { struct icmp6hdr *icmp6; if (!pskb_may_pull(skb, (skb_network_header(skb) + offset + 1 - skb->data))) return 0; icmp6 = (struct icmp6hdr *)(skb_network_header(skb) + offset); switch (icmp6->icmp6_type) { case NDISC_ROUTER_SOLICITATION: case NDISC_ROUTER_ADVERTISEMENT: case NDISC_NEIGHBOUR_SOLICITATION: case NDISC_NEIGHBOUR_ADVERTISEMENT: case NDISC_REDIRECT: /* For reaction involving unicast neighbor discovery * message destined to the proxied address, pass it to * input function. */ return 1; default: break; } } /* * The proxying router can't forward traffic sent to a link-local * address, so signal the sender and discard the packet. This * behavior is clarified by the MIPv6 specification. */ if (ipv6_addr_type(&hdr->daddr) & IPV6_ADDR_LINKLOCAL) { dst_link_failure(skb); return -1; } return 0; }


Ville Nuorvala17491.10%240.00%
Arnaldo Carvalho de Melo115.76%240.00%
Jesse Gross63.14%120.00%

static inline int ip6_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb) { return dst_output(net, sk, skb); }


Linus Torvalds (pre-git)1753.12%120.00%
Eric W. Biedermann825.00%360.00%
David S. Miller721.88%120.00%

static unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst) { unsigned int mtu; struct inet6_dev *idev; if (dst_metric_locked(dst, RTAX_MTU)) { mtu = dst_metric_raw(dst, RTAX_MTU); if (mtu) return mtu; } mtu = IPV6_MIN_MTU; rcu_read_lock(); idev = __in6_dev_get(dst->dev); if (idev) mtu = idev->cnf.mtu6; rcu_read_unlock(); return mtu; }


Hannes Frederic Sowa83100.00%1100.00%

static bool ip6_pkt_too_big(const struct sk_buff *skb, unsigned int mtu) { if (skb->len <= mtu) return false; /* ipv6 conntrack defrag sets max_frag_size + ignore_df */ if (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu) return true; if (skb->ignore_df) return false; if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu)) return false; return true; }


Florian Westphal7393.59%250.00%
Marcelo Ricardo Leitner33.85%125.00%
Américo Wang22.56%125.00%

int ip6_forward(struct sk_buff *skb) { struct dst_entry *dst = skb_dst(skb); struct ipv6hdr *hdr = ipv6_hdr(skb); struct inet6_skb_parm *opt = IP6CB(skb); struct net *net = dev_net(dst->dev); u32 mtu; if (net->ipv6.devconf_all->forwarding == 0) goto error; if (skb->pkt_type != PACKET_HOST) goto drop; if (unlikely(skb->sk)) goto drop; if (skb_warn_if_lro(skb)) goto drop; if (!xfrm6_policy_check(NULL, XFRM_POLICY_FWD, skb)) { __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_INDISCARDS); goto drop; } skb_forward_csum(skb); /* * We DO NOT make any processing on * RA packets, pushing them to user level AS IS * without ane WARRANTY that application will be able * to interpret them. The reason is that we * cannot make anything clever here. * * We are not end-node, so that if packet contains * AH/ESP, we cannot make anything. * Defragmentation also would be mistake, RA packets * cannot be fragmented, because there is no warranty * that different fragments will go along one path. --ANK */ if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) { if (ip6_call_ra_chain(skb, ntohs(opt->ra))) return 0; } /* * check and decrement ttl */ if (hdr->hop_limit <= 1) { /* Force OUTPUT device used as source address */ skb->dev = dst->dev; icmpv6_send(skb, ICMPV6_TIME_EXCEED, ICMPV6_EXC_HOPLIMIT, 0); __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_INHDRERRORS); kfree_skb(skb); return -ETIMEDOUT; } /* XXX: idev->cnf.proxy_ndp? */ if (net->ipv6.devconf_all->proxy_ndp && pneigh_lookup(&nd_tbl, net, &hdr->daddr, skb->dev, 0)) { int proxied = ip6_forward_proxy_check(skb); if (proxied > 0) return ip6_input(skb); else if (proxied < 0) { __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_INDISCARDS); goto drop; } } if (!xfrm6_route_forward(skb)) { __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_INDISCARDS); goto drop; } dst = skb_dst(skb); /* IPv6 specs say nothing about it, but it is clear that we cannot send redirects to source routed frames. We don't send redirects to frames decapsulated from IPsec. */ if (skb->dev == dst->dev && opt->srcrt == 0 && !skb_sec_path(skb)) { struct in6_addr *target = NULL; struct inet_peer *peer; struct rt6_info *rt; /* * incoming and outgoing devices are the same * send a redirect. */ rt = (struct rt6_info *) dst; if (rt->rt6i_flags & RTF_GATEWAY) target = &rt->rt6i_gateway; else target = &hdr->daddr; peer = inet_getpeer_v6(net->ipv6.peers, &hdr->daddr, 1); /* Limit redirects both by destination (here) and by source (inside ndisc_send_redirect) */ if (inet_peer_xrlim_allow(peer, 1*HZ)) ndisc_send_redirect(skb, target); if (peer) inet_putpeer(peer); } else { int addrtype = ipv6_addr_type(&hdr->saddr); /* This check is security critical. */ if (addrtype == IPV6_ADDR_ANY || addrtype & (IPV6_ADDR_MULTICAST | IPV6_ADDR_LOOPBACK)) goto error; if (addrtype & IPV6_ADDR_LINKLOCAL) { icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_NOT_NEIGHBOUR, 0); goto error; } } mtu = ip6_dst_mtu_forward(dst); if (mtu < IPV6_MIN_MTU) mtu = IPV6_MIN_MTU; if (ip6_pkt_too_big(skb, mtu)) { /* Again, force OUTPUT device used as source address */ skb->dev = dst->dev; icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu); __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_INTOOBIGERRORS); __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_FRAGFAILS); kfree_skb(skb); return -EMSGSIZE; } if (skb_cow(skb, dst->dev->hard_header_len)) { __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTDISCARDS); goto drop; } hdr = ipv6_hdr(skb); /* Mangling hops number delayed to point after skb COW */ hdr->hop_limit--; __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTFORWDATAGRAMS); __IP6_ADD_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTOCTETS, skb->len); return NF_HOOK(NFPROTO_IPV6, NF_INET_FORWARD, net, NULL, skb, skb->dev, dst->dev, ip6_forward_finish); error: __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_INADDRERRORS); drop: kfree_skb(skb); return -EINVAL; }


Linus Torvalds (pre-git)28840.91%815.69%
Hideaki Yoshifuji / 吉藤英明8812.50%815.69%
Ville Nuorvala567.95%23.92%
David S. Miller365.11%59.80%
David L Stevens314.40%11.96%
Tom Lendacky263.69%11.96%
Ulrich Weber202.84%11.96%
Shirley Ma182.56%11.96%
Denis V. Lunev182.56%23.92%
Eric Dumazet162.27%23.92%
Vincent Bernat152.13%11.96%
Hannes Frederic Sowa131.85%23.92%
Li RongQing111.56%11.96%
Ben Hutchings101.42%11.96%
Daniel Lezcano101.42%11.96%
Linus Torvalds101.42%11.96%
Herbert Xu70.99%23.92%
Arnaldo Carvalho de Melo60.85%11.96%
Wei Dong40.57%11.96%
Eric W. Biedermann40.57%23.92%
Patrick McHardy40.57%23.92%
Masahide Nakamura40.57%11.96%
Florian Westphal30.43%11.96%
Alexey Dobriyan30.43%11.96%
Martin KaFai Lau20.28%11.96%
Jan Engelhardt10.14%11.96%

static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from) { to->pkt_type = from->pkt_type; to->priority = from->priority; to->protocol = from->protocol; skb_dst_drop(to); skb_dst_set(to, dst_clone(skb_dst(from))); to->dev = from->dev; to->mark = from->mark; #ifdef CONFIG_NET_SCHED to->tc_index = from->tc_index; #endif nf_copy(to, from); skb_copy_secmark(to, from); }


Kazunori Miyazawa7069.31%114.29%
Thomas Graf87.92%114.29%
Eric Dumazet87.92%114.29%
James Morris76.93%114.29%
Yasuyuki Kozakai43.96%228.57%
Hideaki Yoshifuji / 吉藤英明43.96%114.29%

int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, int (*output)(struct net *, struct sock *, struct sk_buff *)) { struct sk_buff *frag; struct rt6_info *rt = (struct rt6_info *)skb_dst(skb); struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ? inet6_sk(skb->sk) : NULL; struct ipv6hdr *tmp_hdr; struct frag_hdr *fh; unsigned int mtu, hlen, left, len; int hroom, troom; __be32 frag_id; int ptr, offset = 0, err = 0; u8 *prevhdr, nexthdr = 0; err = ip6_find_1stfragopt(skb, &prevhdr); if (err < 0) goto fail; hlen = err; nexthdr = *prevhdr; mtu = ip6_skb_dst_mtu(skb); /* We must not fragment if the socket is set to force MTU discovery * or if the skb it not generated by a local socket. */ if (unlikely(!skb->ignore_df && skb->len > mtu)) goto fail_toobig; if (IP6CB(skb)->frag_max_size) { if (IP6CB(skb)->frag_max_size > mtu) goto fail_toobig; /* don't send fragments larger than what we received */ mtu = IP6CB(skb)->frag_max_size; if (mtu < IPV6_MIN_MTU) mtu = IPV6_MIN_MTU; } if (np && np->frag_size < mtu) { if (np->frag_size) mtu = np->frag_size; } if (mtu < hlen + sizeof(struct frag_hdr) + 8) goto fail_toobig; mtu -= hlen + sizeof(struct frag_hdr); frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr, &ipv6_hdr(skb)->saddr); if (skb->ip_summed == CHECKSUM_PARTIAL && (err = skb_checksum_help(skb))) goto fail; hroom = LL_RESERVED_SPACE(rt->; if (skb_has_frag_list(skb)) { unsigned int first_len = skb_pagelen(skb); struct sk_buff *frag2; if (first_len