ebt_log.c

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/*
 *  ebt_log
 *
 *  Authors:
 *  Bart De Schuymer <[email protected]>
 *  Harald Welte <[email protected]>
 *
 *  April, 2002
 *
 */
#include <linux/module.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/if_arp.h>
#include <linux/spinlock.h>
#include <net/netfilter/nf_log.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
#include <linux/in6.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_log.h>
#include <linux/netfilter.h>

static DEFINE_SPINLOCK(ebt_log_lock);

static int ebt_log_tg_check(const struct xt_tgchk_param *par)
{
    struct ebt_log_info *info = par->targinfo;

    if (info->bitmask & ~EBT_LOG_MASK)
        return -EINVAL;
    if (info->loglevel >= 8)
        return -EINVAL;
    info->prefix[EBT_LOG_PREFIX_SIZE - 1] = '\0';
    return 0;
}

struct tcpudphdr
{
    __be16 src;
    __be16 dst;
};

struct arppayload
{
    unsigned char mac_src[ETH_ALEN];
    unsigned char ip_src[4];
    unsigned char mac_dst[ETH_ALEN];
    unsigned char ip_dst[4];
};

static void
print_ports(const struct sk_buff *skb, uint8_t protocol, int offset)
{
    if (protocol == IPPROTO_TCP ||
        protocol == IPPROTO_UDP ||
        protocol == IPPROTO_UDPLITE ||
        protocol == IPPROTO_SCTP ||
        protocol == IPPROTO_DCCP) {
        const struct tcpudphdr *pptr;
        struct tcpudphdr _ports;

        pptr = skb_header_pointer(skb, offset,
                      sizeof(_ports), &_ports);
        if (pptr == NULL) {
            printk(" INCOMPLETE TCP/UDP header");
            return;
        }
        printk(" SPT=%u DPT=%u", ntohs(pptr->src), ntohs(pptr->dst));
    }
}

static void
ebt_log_packet(u_int8_t pf, unsigned int hooknum,
   const struct sk_buff *skb, const struct net_device *in,
   const struct net_device *out, const struct nf_loginfo *loginfo,
   const char *prefix)
{
    unsigned int bitmask;

    spin_lock_bh(&ebt_log_lock);
    printk(KERN_SOH "%c%s IN=%s OUT=%s MAC source = %pM MAC dest = %pM proto = 0x%04x",
           '0' + loginfo->u.log.level, prefix,
           in ? in->name : "", out ? out->name : "",
           eth_hdr(skb)->h_source, eth_hdr(skb)->h_dest,
           ntohs(eth_hdr(skb)->h_proto));

    if (loginfo->type == NF_LOG_TYPE_LOG)
        bitmask = loginfo->u.log.logflags;
    else
        bitmask = NF_LOG_MASK;

    if ((bitmask & EBT_LOG_IP) && eth_hdr(skb)->h_proto ==
       htons(ETH_P_IP)){
        const struct iphdr *ih;
        struct iphdr _iph;

        ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
        if (ih == NULL) {
            printk(" INCOMPLETE IP header");
            goto out;
        }
        printk(" IP SRC=%pI4 IP DST=%pI4, IP tos=0x%02X, IP proto=%d",
               &ih->saddr, &ih->daddr, ih->tos, ih->protocol);
        print_ports(skb, ih->protocol, ih->ihl*4);
        goto out;
    }

#if IS_ENABLED(CONFIG_BRIDGE_EBT_IP6)
    if ((bitmask & EBT_LOG_IP6) && eth_hdr(skb)->h_proto ==
       htons(ETH_P_IPV6)) {
        const struct ipv6hdr *ih;
        struct ipv6hdr _iph;
        uint8_t nexthdr;
        __be16 frag_off;
        int offset_ph;

        ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
        if (ih == NULL) {
            printk(" INCOMPLETE IPv6 header");
            goto out;
        }
        printk(" IPv6 SRC=%pI6 IPv6 DST=%pI6, IPv6 priority=0x%01X, Next Header=%d",
               &ih->saddr, &ih->daddr, ih->priority, ih->nexthdr);
        nexthdr = ih->nexthdr;
        offset_ph = ipv6_skip_exthdr(skb, sizeof(_iph), &nexthdr, &frag_off);
        if (offset_ph == -1)
            goto out;
        print_ports(skb, nexthdr, offset_ph);
        goto out;
    }
#endif

    if ((bitmask & EBT_LOG_ARP) &&
        ((eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) ||
         (eth_hdr(skb)->h_proto == htons(ETH_P_RARP)))) {
        const struct arphdr *ah;
        struct arphdr _arph;

        ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
        if (ah == NULL) {
            printk(" INCOMPLETE ARP header");
            goto out;
        }
        printk(" ARP HTYPE=%d, PTYPE=0x%04x, OPCODE=%d",
               ntohs(ah->ar_hrd), ntohs(ah->ar_pro),
               ntohs(ah->ar_op));

        /* If it's for Ethernet and the lengths are OK,
         * then log the ARP payload */
        if (ah->ar_hrd == htons(1) &&
            ah->ar_hln == ETH_ALEN &&
            ah->ar_pln == sizeof(__be32)) {
            const struct arppayload *ap;
            struct arppayload _arpp;

            ap = skb_header_pointer(skb, sizeof(_arph),
                        sizeof(_arpp), &_arpp);
            if (ap == NULL) {
                printk(" INCOMPLETE ARP payload");
                goto out;
            }
            printk(" ARP MAC SRC=%pM ARP IP SRC=%pI4 ARP MAC DST=%pM ARP IP DST=%pI4",
                    ap->mac_src, ap->ip_src, ap->mac_dst, ap->ip_dst);
        }
    }
out:
    printk("\n");
    spin_unlock_bh(&ebt_log_lock);

}

static unsigned int
ebt_log_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
    const struct ebt_log_info *info = par->targinfo;
    struct nf_loginfo li;

    li.type = NF_LOG_TYPE_LOG;
    li.u.log.level = info->loglevel;
    li.u.log.logflags = info->bitmask;

    if (info->bitmask & EBT_LOG_NFLOG)
        nf_log_packet(NFPROTO_BRIDGE, par->hooknum, skb, par->in,
                      par->out, &li, "%s", info->prefix);
    else
        ebt_log_packet(NFPROTO_BRIDGE, par->hooknum, skb, par->in,
                       par->out, &li, info->prefix);
    return EBT_CONTINUE;
}

static struct xt_target ebt_log_tg_reg __read_mostly = {
    .name       = "log",
    .revision   = 0,
    .family     = NFPROTO_BRIDGE,
    .target     = ebt_log_tg,
    .checkentry = ebt_log_tg_check,
    .targetsize = sizeof(struct ebt_log_info),
    .me     = THIS_MODULE,
};

static struct nf_logger ebt_log_logger __read_mostly = {
    .name       = "ebt_log",
    .logfn      = &ebt_log_packet,
    .me     = THIS_MODULE,
};

static int __init ebt_log_init(void)
{
    int ret;

    ret = xt_register_target(&ebt_log_tg_reg);
    if (ret < 0)
        return ret;
    nf_log_register(NFPROTO_BRIDGE, &ebt_log_logger);
    return 0;
}

static void __exit ebt_log_fini(void)
{
    nf_log_unregister(&ebt_log_logger);
    xt_unregister_target(&ebt_log_tg_reg);
}

module_init(ebt_log_init);
module_exit(ebt_log_fini);
MODULE_DESCRIPTION("Ebtables: Packet logging to syslog");
MODULE_LICENSE("GPL");