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root/net/ipv4/netfilter/ipt_LOG.c

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DEFINITIONS

This source file includes following definitions.
  1. dump_packet
  2. ipt_log_packet
  3. log_tg
  4. log_tg_check
  5. log_tg_init
  6. log_tg_exit

/*
 * This is a module which is used for logging packets.
 */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <net/route.h>

#include <linux/netfilter.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ipt_LOG.h>
#include <net/netfilter/nf_log.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("Xtables: IPv4 packet logging to syslog");

/* Use lock to serialize, so printks don't overlap */
static DEFINE_SPINLOCK(log_lock);

/* One level of recursion won't kill us */
static void dump_packet(const struct nf_loginfo *info,
                        const struct sk_buff *skb,
                        unsigned int iphoff)
{
        struct iphdr _iph;
        const struct iphdr *ih;
        unsigned int logflags;

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

        ih = skb_header_pointer(skb, iphoff, sizeof(_iph), &_iph);
        if (ih == NULL) {
                printk("TRUNCATED");
                return;
        }

        /* Important fields:
         * TOS, len, DF/MF, fragment offset, TTL, src, dst, options. */
        /* Max length: 40 "SRC=255.255.255.255 DST=255.255.255.255 " */
        printk("SRC=%u.%u.%u.%u DST=%u.%u.%u.%u ",
               NIPQUAD(ih->saddr), NIPQUAD(ih->daddr));

        /* Max length: 46 "LEN=65535 TOS=0xFF PREC=0xFF TTL=255 ID=65535 " */
        printk("LEN=%u TOS=0x%02X PREC=0x%02X TTL=%u ID=%u ",
               ntohs(ih->tot_len), ih->tos & IPTOS_TOS_MASK,
               ih->tos & IPTOS_PREC_MASK, ih->ttl, ntohs(ih->id));

        /* Max length: 6 "CE DF MF " */
        if (ntohs(ih->frag_off) & IP_CE)
                printk("CE ");
        if (ntohs(ih->frag_off) & IP_DF)
                printk("DF ");
        if (ntohs(ih->frag_off) & IP_MF)
                printk("MF ");

        /* Max length: 11 "FRAG:65535 " */
        if (ntohs(ih->frag_off) & IP_OFFSET)
                printk("FRAG:%u ", ntohs(ih->frag_off) & IP_OFFSET);

        if ((logflags & IPT_LOG_IPOPT)
            && ih->ihl * 4 > sizeof(struct iphdr)) {
                const unsigned char *op;
                unsigned char _opt[4 * 15 - sizeof(struct iphdr)];
                unsigned int i, optsize;

                optsize = ih->ihl * 4 - sizeof(struct iphdr);
                op = skb_header_pointer(skb, iphoff+sizeof(_iph),
                                        optsize, _opt);
                if (op == NULL) {
                        printk("TRUNCATED");
                        return;
                }

                /* Max length: 127 "OPT (" 15*4*2chars ") " */
                printk("OPT (");
                for (i = 0; i < optsize; i++)
                        printk("%02X", op[i]);
                printk(") ");
        }

        switch (ih->protocol) {
        case IPPROTO_TCP: {
                struct tcphdr _tcph;
                const struct tcphdr *th;

                /* Max length: 10 "PROTO=TCP " */
                printk("PROTO=TCP ");

                if (ntohs(ih->frag_off) & IP_OFFSET)
                        break;

                /* Max length: 25 "INCOMPLETE [65535 bytes] " */
                th = skb_header_pointer(skb, iphoff + ih->ihl * 4,
                                        sizeof(_tcph), &_tcph);
                if (th == NULL) {
                        printk("INCOMPLETE [%u bytes] ",
                               skb->len - iphoff - ih->ihl*4);
                        break;
                }

                /* Max length: 20 "SPT=65535 DPT=65535 " */
                printk("SPT=%u DPT=%u ",
                       ntohs(th->source), ntohs(th->dest));
                /* Max length: 30 "SEQ=4294967295 ACK=4294967295 " */
                if (logflags & IPT_LOG_TCPSEQ)
                        printk("SEQ=%u ACK=%u ",
                               ntohl(th->seq), ntohl(th->ack_seq));
                /* Max length: 13 "WINDOW=65535 " */
                printk("WINDOW=%u ", ntohs(th->window));
                /* Max length: 9 "RES=0x3F " */
                printk("RES=0x%02x ", (u8)(ntohl(tcp_flag_word(th) & TCP_RESERVED_BITS) >> 22));
                /* Max length: 32 "CWR ECE URG ACK PSH RST SYN FIN " */
                if (th->cwr)
                        printk("CWR ");
                if (th->ece)
                        printk("ECE ");
                if (th->urg)
                        printk("URG ");
                if (th->ack)
                        printk("ACK ");
                if (th->psh)
                        printk("PSH ");
                if (th->rst)
                        printk("RST ");
                if (th->syn)
                        printk("SYN ");
                if (th->fin)
                        printk("FIN ");
                /* Max length: 11 "URGP=65535 " */
                printk("URGP=%u ", ntohs(th->urg_ptr));

                if ((logflags & IPT_LOG_TCPOPT)
                    && th->doff * 4 > sizeof(struct tcphdr)) {
                        unsigned char _opt[4 * 15 - sizeof(struct tcphdr)];
                        const unsigned char *op;
                        unsigned int i, optsize;

                        optsize = th->doff * 4 - sizeof(struct tcphdr);
                        op = skb_header_pointer(skb,
                                                iphoff+ih->ihl*4+sizeof(_tcph),
                                                optsize, _opt);
                        if (op == NULL) {
                                printk("TRUNCATED");
                                return;
                        }

                        /* Max length: 127 "OPT (" 15*4*2chars ") " */
                        printk("OPT (");
                        for (i = 0; i < optsize; i++)
                                printk("%02X", op[i]);
                        printk(") ");
                }
                break;
        }
        case IPPROTO_UDP:
        case IPPROTO_UDPLITE: {
                struct udphdr _udph;
                const struct udphdr *uh;

                if (ih->protocol == IPPROTO_UDP)
                        /* Max length: 10 "PROTO=UDP "     */
                        printk("PROTO=UDP " );
                else    /* Max length: 14 "PROTO=UDPLITE " */
                        printk("PROTO=UDPLITE ");

                if (ntohs(ih->frag_off) & IP_OFFSET)
                        break;

                /* Max length: 25 "INCOMPLETE [65535 bytes] " */
                uh = skb_header_pointer(skb, iphoff+ih->ihl*4,
                                        sizeof(_udph), &_udph);
                if (uh == NULL) {
                        printk("INCOMPLETE [%u bytes] ",
                               skb->len - iphoff - ih->ihl*4);
                        break;
                }

                /* Max length: 20 "SPT=65535 DPT=65535 " */
                printk("SPT=%u DPT=%u LEN=%u ",
                       ntohs(uh->source), ntohs(uh->dest),
                       ntohs(uh->len));
                break;
        }
        case IPPROTO_ICMP: {
                struct icmphdr _icmph;
                const struct icmphdr *ich;
                static const size_t required_len[NR_ICMP_TYPES+1]
                        = { [ICMP_ECHOREPLY] = 4,
                            [ICMP_DEST_UNREACH]
                            = 8 + sizeof(struct iphdr),
                            [ICMP_SOURCE_QUENCH]
                            = 8 + sizeof(struct iphdr),
                            [ICMP_REDIRECT]
                            = 8 + sizeof(struct iphdr),
                            [ICMP_ECHO] = 4,
                            [ICMP_TIME_EXCEEDED]
                            = 8 + sizeof(struct iphdr),
                            [ICMP_PARAMETERPROB]
                            = 8 + sizeof(struct iphdr),
                            [ICMP_TIMESTAMP] = 20,
                            [ICMP_TIMESTAMPREPLY] = 20,
                            [ICMP_ADDRESS] = 12,
                            [ICMP_ADDRESSREPLY] = 12 };

                /* Max length: 11 "PROTO=ICMP " */
                printk("PROTO=ICMP ");

                if (ntohs(ih->frag_off) & IP_OFFSET)
                        break;

                /* Max length: 25 "INCOMPLETE [65535 bytes] " */
                ich = skb_header_pointer(skb, iphoff + ih->ihl * 4,
                                         sizeof(_icmph), &_icmph);
                if (ich == NULL) {
                        printk("INCOMPLETE [%u bytes] ",
                               skb->len - iphoff - ih->ihl*4);
                        break;
                }

                /* Max length: 18 "TYPE=255 CODE=255 " */
                printk("TYPE=%u CODE=%u ", ich->type, ich->code);

                /* Max length: 25 "INCOMPLETE [65535 bytes] " */
                if (ich->type <= NR_ICMP_TYPES
                    && required_len[ich->type]
                    && skb->len-iphoff-ih->ihl*4 < required_len[ich->type]) {
                        printk("INCOMPLETE [%u bytes] ",
                               skb->len - iphoff - ih->ihl*4);
                        break;
                }

                switch (ich->type) {
                case ICMP_ECHOREPLY:
                case ICMP_ECHO:
                        /* Max length: 19 "ID=65535 SEQ=65535 " */
                        printk("ID=%u SEQ=%u ",
                               ntohs(ich->un.echo.id),
                               ntohs(ich->un.echo.sequence));
                        break;

                case ICMP_PARAMETERPROB:
                        /* Max length: 14 "PARAMETER=255 " */
                        printk("PARAMETER=%u ",
                               ntohl(ich->un.gateway) >> 24);
                        break;
                case ICMP_REDIRECT:
                        /* Max length: 24 "GATEWAY=255.255.255.255 " */
                        printk("GATEWAY=%u.%u.%u.%u ",
                               NIPQUAD(ich->un.gateway));
                        /* Fall through */
                case ICMP_DEST_UNREACH:
                case ICMP_SOURCE_QUENCH:
                case ICMP_TIME_EXCEEDED:
                        /* Max length: 3+maxlen */
                        if (!iphoff) { /* Only recurse once. */
                                printk("[");
                                dump_packet(info, skb,
                                            iphoff + ih->ihl*4+sizeof(_icmph));
                                printk("] ");
                        }

                        /* Max length: 10 "MTU=65535 " */
                        if (ich->type == ICMP_DEST_UNREACH
                            && ich->code == ICMP_FRAG_NEEDED)
                                printk("MTU=%u ", ntohs(ich->un.frag.mtu));
                }
                break;
        }
        /* Max Length */
        case IPPROTO_AH: {
                struct ip_auth_hdr _ahdr;
                const struct ip_auth_hdr *ah;

                if (ntohs(ih->frag_off) & IP_OFFSET)
                        break;

                /* Max length: 9 "PROTO=AH " */
                printk("PROTO=AH ");

                /* Max length: 25 "INCOMPLETE [65535 bytes] " */
                ah = skb_header_pointer(skb, iphoff+ih->ihl*4,
                                        sizeof(_ahdr), &_ahdr);
                if (ah == NULL) {
                        printk("INCOMPLETE [%u bytes] ",
                               skb->len - iphoff - ih->ihl*4);
                        break;
                }

                /* Length: 15 "SPI=0xF1234567 " */
                printk("SPI=0x%x ", ntohl(ah->spi));
                break;
        }
        case IPPROTO_ESP: {
                struct ip_esp_hdr _esph;
                const struct ip_esp_hdr *eh;

                /* Max length: 10 "PROTO=ESP " */
                printk("PROTO=ESP ");

                if (ntohs(ih->frag_off) & IP_OFFSET)
                        break;

                /* Max length: 25 "INCOMPLETE [65535 bytes] " */
                eh = skb_header_pointer(skb, iphoff+ih->ihl*4,
                                        sizeof(_esph), &_esph);
                if (eh == NULL) {
                        printk("INCOMPLETE [%u bytes] ",
                               skb->len - iphoff - ih->ihl*4);
                        break;
                }

                /* Length: 15 "SPI=0xF1234567 " */
                printk("SPI=0x%x ", ntohl(eh->spi));
                break;
        }
        /* Max length: 10 "PROTO 255 " */
        default:
                printk("PROTO=%u ", ih->protocol);
        }

        /* Max length: 15 "UID=4294967295 " */
        if ((logflags & IPT_LOG_UID) && !iphoff && skb->sk) {
                read_lock_bh(&skb->sk->sk_callback_lock);
                if (skb->sk->sk_socket && skb->sk->sk_socket->file)
                        printk("UID=%u GID=%u ",
                                skb->sk->sk_socket->file->f_uid,
                                skb->sk->sk_socket->file->f_gid);
                read_unlock_bh(&skb->sk->sk_callback_lock);
        }

        /* Max length: 16 "MARK=0xFFFFFFFF " */
        if (!iphoff && skb->mark)
                printk("MARK=0x%x ", skb->mark);

        /* Proto    Max log string length */
        /* IP:      40+46+6+11+127 = 230 */
        /* TCP:     10+max(25,20+30+13+9+32+11+127) = 252 */
        /* UDP:     10+max(25,20) = 35 */
        /* UDPLITE: 14+max(25,20) = 39 */
        /* ICMP:    11+max(25, 18+25+max(19,14,24+3+n+10,3+n+10)) = 91+n */
        /* ESP:     10+max(25)+15 = 50 */
        /* AH:      9+max(25)+15 = 49 */
        /* unknown: 10 */

        /* (ICMP allows recursion one level deep) */
        /* maxlen =  IP + ICMP +  IP + max(TCP,UDP,ICMP,unknown) */
        /* maxlen = 230+   91  + 230 + 252 = 803 */
}

static struct nf_loginfo default_loginfo = {
        .type   = NF_LOG_TYPE_LOG,
        .u = {
                .log = {
                        .level    = 0,
                        .logflags = NF_LOG_MASK,
                },
        },
};

static void
ipt_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)
{
        if (!loginfo)
                loginfo = &default_loginfo;

        spin_lock_bh(&log_lock);
        printk("<%d>%sIN=%s OUT=%s ", loginfo->u.log.level,
               prefix,
               in ? in->name : "",
               out ? out->name : "");
#ifdef CONFIG_BRIDGE_NETFILTER
        if (skb->nf_bridge) {
                const struct net_device *physindev;
                const struct net_device *physoutdev;

                physindev = skb->nf_bridge->physindev;
                if (physindev && in != physindev)
                        printk("PHYSIN=%s ", physindev->name);
                physoutdev = skb->nf_bridge->physoutdev;
                if (physoutdev && out != physoutdev)
                        printk("PHYSOUT=%s ", physoutdev->name);
        }
#endif

        if (in && !out) {
                /* MAC logging for input chain only. */
                printk("MAC=");
                if (skb->dev && skb->dev->hard_header_len
                    && skb->mac_header != skb->network_header) {
                        int i;
                        const unsigned char *p = skb_mac_header(skb);
                        for (i = 0; i < skb->dev->hard_header_len; i++,p++)
                                printk("%02x%c", *p,
                                       i==skb->dev->hard_header_len - 1
                                       ? ' ':':');
                } else
                        printk(" ");
        }

        dump_packet(loginfo, skb, 0);
        printk("\n");
        spin_unlock_bh(&log_lock);
}

static unsigned int
log_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
        const struct ipt_log_info *loginfo = par->targinfo;
        struct nf_loginfo li;

        li.type = NF_LOG_TYPE_LOG;
        li.u.log.level = loginfo->level;
        li.u.log.logflags = loginfo->logflags;

        ipt_log_packet(NFPROTO_IPV4, par->hooknum, skb, par->in, par->out, &li,
                       loginfo->prefix);
        return XT_CONTINUE;
}

static bool log_tg_check(const struct xt_tgchk_param *par)
{
        const struct ipt_log_info *loginfo = par->targinfo;

        if (loginfo->level >= 8) {
                pr_debug("LOG: level %u >= 8\n", loginfo->level);
                return false;
        }
        if (loginfo->prefix[sizeof(loginfo->prefix)-1] != '\0') {
                pr_debug("LOG: prefix term %i\n",
                         loginfo->prefix[sizeof(loginfo->prefix)-1]);
                return false;
        }
        return true;
}

static struct xt_target log_tg_reg __read_mostly = {
        .name           = "LOG",
        .family         = NFPROTO_IPV4,
        .target         = log_tg,
        .targetsize     = sizeof(struct ipt_log_info),
        .checkentry     = log_tg_check,
        .me             = THIS_MODULE,
};

static const struct nf_logger ipt_log_logger ={
        .name           = "ipt_LOG",
        .logfn          = &ipt_log_packet,
        .me             = THIS_MODULE,
};

static int __init log_tg_init(void)
{
        int ret;

        ret = xt_register_target(&log_tg_reg);
        if (ret < 0)
                return ret;
        nf_log_register(NFPROTO_IPV4, &ipt_log_logger);
        return 0;
}

static void __exit log_tg_exit(void)
{
        nf_log_unregister(&ipt_log_logger);
        xt_unregister_target(&log_tg_reg);
}

module_init(log_tg_init);
module_exit(log_tg_exit);

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