act_csum.c

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/*
 * Checksum updating actions
 *
 * Copyright (c) 2010 Gregoire Baron <[email protected]>
 *
 * 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.
 *
 */

#include <linux/types.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spinlock.h>

#include <linux/netlink.h>
#include <net/netlink.h>
#include <linux/rtnetlink.h>

#include <linux/skbuff.h>

#include <net/ip.h>
#include <net/ipv6.h>
#include <net/icmp.h>
#include <linux/icmpv6.h>
#include <linux/igmp.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/ip6_checksum.h>

#include <net/act_api.h>

#include <linux/tc_act/tc_csum.h>
#include <net/tc_act/tc_csum.h>

#define CSUM_TAB_MASK 15
static struct tcf_common *tcf_csum_ht[CSUM_TAB_MASK + 1];
static u32 csum_idx_gen;
static DEFINE_RWLOCK(csum_lock);

static struct tcf_hashinfo csum_hash_info = {
    .htab   = tcf_csum_ht,
    .hmask  = CSUM_TAB_MASK,
    .lock   = &csum_lock,
};

static const struct nla_policy csum_policy[TCA_CSUM_MAX + 1] = {
    [TCA_CSUM_PARMS] = { .len = sizeof(struct tc_csum), },
};

static int tcf_csum_init(struct nlattr *nla, struct nlattr *est,
             struct tc_action *a, int ovr, int bind)
{
    struct nlattr *tb[TCA_CSUM_MAX + 1];
    struct tc_csum *parm;
    struct tcf_common *pc;
    struct tcf_csum *p;
    int ret = 0, err;

    if (nla == NULL)
        return -EINVAL;

    err = nla_parse_nested(tb, TCA_CSUM_MAX, nla, csum_policy);
    if (err < 0)
        return err;

    if (tb[TCA_CSUM_PARMS] == NULL)
        return -EINVAL;
    parm = nla_data(tb[TCA_CSUM_PARMS]);

    pc = tcf_hash_check(parm->index, a, bind, &csum_hash_info);
    if (!pc) {
        pc = tcf_hash_create(parm->index, est, a, sizeof(*p), bind,
                     &csum_idx_gen, &csum_hash_info);
        if (IS_ERR(pc))
            return PTR_ERR(pc);
        p = to_tcf_csum(pc);
        ret = ACT_P_CREATED;
    } else {
        p = to_tcf_csum(pc);
        if (!ovr) {
            tcf_hash_release(pc, bind, &csum_hash_info);
            return -EEXIST;
        }
    }

    spin_lock_bh(&p->tcf_lock);
    p->tcf_action = parm->action;
    p->update_flags = parm->update_flags;
    spin_unlock_bh(&p->tcf_lock);

    if (ret == ACT_P_CREATED)
        tcf_hash_insert(pc, &csum_hash_info);

    return ret;
}

static int tcf_csum_cleanup(struct tc_action *a, int bind)
{
    struct tcf_csum *p = a->priv;
    return tcf_hash_release(&p->common, bind, &csum_hash_info);
}

static void *tcf_csum_skb_nextlayer(struct sk_buff *skb,
                    unsigned int ihl, unsigned int ipl,
                    unsigned int jhl)
{
    int ntkoff = skb_network_offset(skb);
    int hl = ihl + jhl;

    if (!pskb_may_pull(skb, ipl + ntkoff) || (ipl < hl) ||
        (skb_cloned(skb) &&
         !skb_clone_writable(skb, hl + ntkoff) &&
         pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
        return NULL;
    else
        return (void *)(skb_network_header(skb) + ihl);
}

static int tcf_csum_ipv4_icmp(struct sk_buff *skb,
                  unsigned int ihl, unsigned int ipl)
{
    struct icmphdr *icmph;

    icmph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*icmph));
    if (icmph == NULL)
        return 0;

    icmph->checksum = 0;
    skb->csum = csum_partial(icmph, ipl - ihl, 0);
    icmph->checksum = csum_fold(skb->csum);

    skb->ip_summed = CHECKSUM_NONE;

    return 1;
}

static int tcf_csum_ipv4_igmp(struct sk_buff *skb,
                  unsigned int ihl, unsigned int ipl)
{
    struct igmphdr *igmph;

    igmph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*igmph));
    if (igmph == NULL)
        return 0;

    igmph->csum = 0;
    skb->csum = csum_partial(igmph, ipl - ihl, 0);
    igmph->csum = csum_fold(skb->csum);

    skb->ip_summed = CHECKSUM_NONE;

    return 1;
}

static int tcf_csum_ipv6_icmp(struct sk_buff *skb, struct ipv6hdr *ip6h,
                  unsigned int ihl, unsigned int ipl)
{
    struct icmp6hdr *icmp6h;

    icmp6h = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*icmp6h));
    if (icmp6h == NULL)
        return 0;

    icmp6h->icmp6_cksum = 0;
    skb->csum = csum_partial(icmp6h, ipl - ihl, 0);
    icmp6h->icmp6_cksum = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
                          ipl - ihl, IPPROTO_ICMPV6,
                          skb->csum);

    skb->ip_summed = CHECKSUM_NONE;

    return 1;
}

static int tcf_csum_ipv4_tcp(struct sk_buff *skb, struct iphdr *iph,
                 unsigned int ihl, unsigned int ipl)
{
    struct tcphdr *tcph;

    tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
    if (tcph == NULL)
        return 0;

    tcph->check = 0;
    skb->csum = csum_partial(tcph, ipl - ihl, 0);
    tcph->check = tcp_v4_check(ipl - ihl,
                   iph->saddr, iph->daddr, skb->csum);

    skb->ip_summed = CHECKSUM_NONE;

    return 1;
}

static int tcf_csum_ipv6_tcp(struct sk_buff *skb, struct ipv6hdr *ip6h,
                 unsigned int ihl, unsigned int ipl)
{
    struct tcphdr *tcph;

    tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
    if (tcph == NULL)
        return 0;

    tcph->check = 0;
    skb->csum = csum_partial(tcph, ipl - ihl, 0);
    tcph->check = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
                      ipl - ihl, IPPROTO_TCP,
                      skb->csum);

    skb->ip_summed = CHECKSUM_NONE;

    return 1;
}

static int tcf_csum_ipv4_udp(struct sk_buff *skb, struct iphdr *iph,
                 unsigned int ihl, unsigned int ipl, int udplite)
{
    struct udphdr *udph;
    u16 ul;

    /*
     * Support both UDP and UDPLITE checksum algorithms, Don't use
     * udph->len to get the real length without any protocol check,
     * UDPLITE uses udph->len for another thing,
     * Use iph->tot_len, or just ipl.
     */

    udph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*udph));
    if (udph == NULL)
        return 0;

    ul = ntohs(udph->len);

    if (udplite || udph->check) {

        udph->check = 0;

        if (udplite) {
            if (ul == 0)
                skb->csum = csum_partial(udph, ipl - ihl, 0);
            else if ((ul >= sizeof(*udph)) && (ul <= ipl - ihl))
                skb->csum = csum_partial(udph, ul, 0);
            else
                goto ignore_obscure_skb;
        } else {
            if (ul != ipl - ihl)
                goto ignore_obscure_skb;

            skb->csum = csum_partial(udph, ul, 0);
        }

        udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
                        ul, iph->protocol,
                        skb->csum);

        if (!udph->check)
            udph->check = CSUM_MANGLED_0;
    }

    skb->ip_summed = CHECKSUM_NONE;

ignore_obscure_skb:
    return 1;
}

static int tcf_csum_ipv6_udp(struct sk_buff *skb, struct ipv6hdr *ip6h,
                 unsigned int ihl, unsigned int ipl, int udplite)
{
    struct udphdr *udph;
    u16 ul;

    /*
     * Support both UDP and UDPLITE checksum algorithms, Don't use
     * udph->len to get the real length without any protocol check,
     * UDPLITE uses udph->len for another thing,
     * Use ip6h->payload_len + sizeof(*ip6h) ... , or just ipl.
     */

    udph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*udph));
    if (udph == NULL)
        return 0;

    ul = ntohs(udph->len);

    udph->check = 0;

    if (udplite) {
        if (ul == 0)
            skb->csum = csum_partial(udph, ipl - ihl, 0);

        else if ((ul >= sizeof(*udph)) && (ul <= ipl - ihl))
            skb->csum = csum_partial(udph, ul, 0);

        else
            goto ignore_obscure_skb;
    } else {
        if (ul != ipl - ihl)
            goto ignore_obscure_skb;

        skb->csum = csum_partial(udph, ul, 0);
    }

    udph->check = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr, ul,
                      udplite ? IPPROTO_UDPLITE : IPPROTO_UDP,
                      skb->csum);

    if (!udph->check)
        udph->check = CSUM_MANGLED_0;

    skb->ip_summed = CHECKSUM_NONE;

ignore_obscure_skb:
    return 1;
}

static int tcf_csum_ipv4(struct sk_buff *skb, u32 update_flags)
{
    struct iphdr *iph;
    int ntkoff;

    ntkoff = skb_network_offset(skb);

    if (!pskb_may_pull(skb, sizeof(*iph) + ntkoff))
        goto fail;

    iph = ip_hdr(skb);

    switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
    case IPPROTO_ICMP:
        if (update_flags & TCA_CSUM_UPDATE_FLAG_ICMP)
            if (!tcf_csum_ipv4_icmp(skb, iph->ihl * 4,
                        ntohs(iph->tot_len)))
                goto fail;
        break;
    case IPPROTO_IGMP:
        if (update_flags & TCA_CSUM_UPDATE_FLAG_IGMP)
            if (!tcf_csum_ipv4_igmp(skb, iph->ihl * 4,
                        ntohs(iph->tot_len)))
                goto fail;
        break;
    case IPPROTO_TCP:
        if (update_flags & TCA_CSUM_UPDATE_FLAG_TCP)
            if (!tcf_csum_ipv4_tcp(skb, iph, iph->ihl * 4,
                           ntohs(iph->tot_len)))
                goto fail;
        break;
    case IPPROTO_UDP:
        if (update_flags & TCA_CSUM_UPDATE_FLAG_UDP)
            if (!tcf_csum_ipv4_udp(skb, iph, iph->ihl * 4,
                           ntohs(iph->tot_len), 0))
                goto fail;
        break;
    case IPPROTO_UDPLITE:
        if (update_flags & TCA_CSUM_UPDATE_FLAG_UDPLITE)
            if (!tcf_csum_ipv4_udp(skb, iph, iph->ihl * 4,
                           ntohs(iph->tot_len), 1))
                goto fail;
        break;
    }

    if (update_flags & TCA_CSUM_UPDATE_FLAG_IPV4HDR) {
        if (skb_cloned(skb) &&
            !skb_clone_writable(skb, sizeof(*iph) + ntkoff) &&
            pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
            goto fail;

        ip_send_check(iph);
    }

    return 1;

fail:
    return 0;
}

static int tcf_csum_ipv6_hopopts(struct ipv6_opt_hdr *ip6xh,
                 unsigned int ixhl, unsigned int *pl)
{
    int off, len, optlen;
    unsigned char *xh = (void *)ip6xh;

    off = sizeof(*ip6xh);
    len = ixhl - off;

    while (len > 1) {
        switch (xh[off]) {
        case IPV6_TLV_PAD1:
            optlen = 1;
            break;
        case IPV6_TLV_JUMBO:
            optlen = xh[off + 1] + 2;
            if (optlen != 6 || len < 6 || (off & 3) != 2)
                /* wrong jumbo option length/alignment */
                return 0;
            *pl = ntohl(*(__be32 *)(xh + off + 2));
            goto done;
        default:
            optlen = xh[off + 1] + 2;
            if (optlen > len)
                /* ignore obscure options */
                goto done;
            break;
        }
        off += optlen;
        len -= optlen;
    }

done:
    return 1;
}

static int tcf_csum_ipv6(struct sk_buff *skb, u32 update_flags)
{
    struct ipv6hdr *ip6h;
    struct ipv6_opt_hdr *ip6xh;
    unsigned int hl, ixhl;
    unsigned int pl;
    int ntkoff;
    u8 nexthdr;

    ntkoff = skb_network_offset(skb);

    hl = sizeof(*ip6h);

    if (!pskb_may_pull(skb, hl + ntkoff))
        goto fail;

    ip6h = ipv6_hdr(skb);

    pl = ntohs(ip6h->payload_len);
    nexthdr = ip6h->nexthdr;

    do {
        switch (nexthdr) {
        case NEXTHDR_FRAGMENT:
            goto ignore_skb;
        case NEXTHDR_ROUTING:
        case NEXTHDR_HOP:
        case NEXTHDR_DEST:
            if (!pskb_may_pull(skb, hl + sizeof(*ip6xh) + ntkoff))
                goto fail;
            ip6xh = (void *)(skb_network_header(skb) + hl);
            ixhl = ipv6_optlen(ip6xh);
            if (!pskb_may_pull(skb, hl + ixhl + ntkoff))
                goto fail;
            if ((nexthdr == NEXTHDR_HOP) &&
                !(tcf_csum_ipv6_hopopts(ip6xh, ixhl, &pl)))
                goto fail;
            nexthdr = ip6xh->nexthdr;
            hl += ixhl;
            break;
        case IPPROTO_ICMPV6:
            if (update_flags & TCA_CSUM_UPDATE_FLAG_ICMP)
                if (!tcf_csum_ipv6_icmp(skb, ip6h,
                            hl, pl + sizeof(*ip6h)))
                    goto fail;
            goto done;
        case IPPROTO_TCP:
            if (update_flags & TCA_CSUM_UPDATE_FLAG_TCP)
                if (!tcf_csum_ipv6_tcp(skb, ip6h,
                               hl, pl + sizeof(*ip6h)))
                    goto fail;
            goto done;
        case IPPROTO_UDP:
            if (update_flags & TCA_CSUM_UPDATE_FLAG_UDP)
                if (!tcf_csum_ipv6_udp(skb, ip6h, hl,
                               pl + sizeof(*ip6h), 0))
                    goto fail;
            goto done;
        case IPPROTO_UDPLITE:
            if (update_flags & TCA_CSUM_UPDATE_FLAG_UDPLITE)
                if (!tcf_csum_ipv6_udp(skb, ip6h, hl,
                               pl + sizeof(*ip6h), 1))
                    goto fail;
            goto done;
        default:
            goto ignore_skb;
        }
    } while (pskb_may_pull(skb, hl + 1 + ntkoff));

done:
ignore_skb:
    return 1;

fail:
    return 0;
}

static int tcf_csum(struct sk_buff *skb,
            const struct tc_action *a, struct tcf_result *res)
{
    struct tcf_csum *p = a->priv;
    int action;
    u32 update_flags;

    spin_lock(&p->tcf_lock);
    p->tcf_tm.lastuse = jiffies;
    bstats_update(&p->tcf_bstats, skb);
    action = p->tcf_action;
    update_flags = p->update_flags;
    spin_unlock(&p->tcf_lock);

    if (unlikely(action == TC_ACT_SHOT))
        goto drop;

    switch (skb->protocol) {
    case cpu_to_be16(ETH_P_IP):
        if (!tcf_csum_ipv4(skb, update_flags))
            goto drop;
        break;
    case cpu_to_be16(ETH_P_IPV6):
        if (!tcf_csum_ipv6(skb, update_flags))
            goto drop;
        break;
    }

    return action;

drop:
    spin_lock(&p->tcf_lock);
    p->tcf_qstats.drops++;
    spin_unlock(&p->tcf_lock);
    return TC_ACT_SHOT;
}

static int tcf_csum_dump(struct sk_buff *skb,
             struct tc_action *a, int bind, int ref)
{
    unsigned char *b = skb_tail_pointer(skb);
    struct tcf_csum *p = a->priv;
    struct tc_csum opt = {
        .update_flags = p->update_flags,
        .index   = p->tcf_index,
        .action  = p->tcf_action,
        .refcnt  = p->tcf_refcnt - ref,
        .bindcnt = p->tcf_bindcnt - bind,
    };
    struct tcf_t t;

    if (nla_put(skb, TCA_CSUM_PARMS, sizeof(opt), &opt))
        goto nla_put_failure;
    t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install);
    t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse);
    t.expires = jiffies_to_clock_t(p->tcf_tm.expires);
    if (nla_put(skb, TCA_CSUM_TM, sizeof(t), &t))
        goto nla_put_failure;

    return skb->len;

nla_put_failure:
    nlmsg_trim(skb, b);
    return -1;
}

static struct tc_action_ops act_csum_ops = {
    .kind       = "csum",
    .hinfo      = &csum_hash_info,
    .type       = TCA_ACT_CSUM,
    .capab      = TCA_CAP_NONE,
    .owner      = THIS_MODULE,
    .act        = tcf_csum,
    .dump       = tcf_csum_dump,
    .cleanup    = tcf_csum_cleanup,
    .lookup     = tcf_hash_search,
    .init       = tcf_csum_init,
    .walk       = tcf_generic_walker
};

MODULE_DESCRIPTION("Checksum updating actions");
MODULE_LICENSE("GPL");

static int __init csum_init_module(void)
{
    return tcf_register_action(&act_csum_ops);
}

static void __exit csum_cleanup_module(void)
{
    tcf_unregister_action(&act_csum_ops);
}

module_init(csum_init_module);
module_exit(csum_cleanup_module);