/*      $NetBSD: npfd_log.c,v 1.14 2022/04/30 13:20:09 christos Exp $   */

/*-
 * Copyright (c) 2015 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Mindaugas Rasiukevicius.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__RCSID("$NetBSD: npfd_log.c,v 1.14 2022/04/30 13:20:09 christos Exp $");

#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>

#include <net/if.h>

#include <stdio.h>
#include <string.h>
#include <err.h>
#include <inttypes.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include <stdbool.h>

#include <pcap/pcap.h>
#include "npfd.h"

struct npfd_log {
        char ifname[IFNAMSIZ];
        char path[MAXPATHLEN];
        char *filter;
        int snaplen;
        pcap_t *pcap;
        pcap_dumper_t *dumper;
};

static void
npfd_log_setfilter(npfd_log_t *ctx)
{
        struct bpf_program bprog;

        if (ctx->filter == NULL)
                return;

        if (pcap_compile(ctx->pcap, &bprog, ctx->filter, 1, 0) == -1)
                errx(EXIT_FAILURE, "pcap_compile failed for `%s': %s",
                    ctx->filter, pcap_geterr(ctx->pcap));
        if (pcap_setfilter(ctx->pcap, &bprog) == -1)
                errx(EXIT_FAILURE, "pcap_setfilter failed: %s",
                    pcap_geterr(ctx->pcap));
        pcap_freecode(&bprog);
}

static FILE *
npfd_log_gethdr(npfd_log_t *ctx, struct pcap_file_header*hdr)
{
        FILE *fp = fopen(ctx->path, "r");

        hdr->magic = 0;
        if (fp == NULL)
                return NULL;

#define TCPDUMP_MAGIC 0xa1b2c3d4

        switch (fread(hdr, sizeof(*hdr), 1, fp)) {
        case 0:
                hdr->magic = 0;
                fclose(fp);
                return NULL;
        case 1:
                if (hdr->magic != TCPDUMP_MAGIC ||
                    hdr->version_major != PCAP_VERSION_MAJOR ||
                    hdr->version_minor != PCAP_VERSION_MINOR ||
                    hdr->sigfigs != (u_int)pcap_get_tstamp_precision(ctx->pcap))
                        goto out;
                break;
        default:
                goto out;
        }

        return fp;
out:
        fclose(fp);
        hdr->magic = (uint32_t)-1;
        return NULL;
}

static int
npfd_log_getsnaplen(npfd_log_t *ctx)
{
        struct pcap_file_header hdr;
        FILE *fp = npfd_log_gethdr(ctx, &hdr);
        if (fp == NULL)
                return hdr.magic == (uint32_t)-1 ? -1 : 0;
        fclose(fp);
        return hdr.snaplen;
}

static int
npfd_log_validate(npfd_log_t *ctx)
{
        struct pcap_file_header hdr;
        FILE *fp = npfd_log_gethdr(ctx, &hdr);
        size_t o, no;

        if (fp == NULL) {
                if (hdr.magic == 0)
                        return 0;
                goto rename;
        }

        struct stat st;
        if (fstat(fileno(fp), &st) == -1)
                goto rename;

        size_t count = 0;
        for (o = sizeof(hdr);; count++) {
                struct {
                        uint32_t sec;
                        uint32_t usec;
                        uint32_t caplen;
                        uint32_t len;
                } pkt;
                switch (fread(&pkt, sizeof(pkt), 1, fp)) {
                case 0:
                        syslog(LOG_INFO, "%zu packets read from `%s'", count,
                            ctx->path);
                        fclose(fp);
                        return hdr.snaplen;
                case 1:
                        no = o + sizeof(pkt) + pkt.caplen;
                        if (pkt.caplen > hdr.snaplen)
                                goto fix;
                        if (no > (size_t)st.st_size)
                                goto fix;
                        if (fseeko(fp, pkt.caplen, SEEK_CUR) != 0)
                                goto fix;
                        o = no;
                        break;
                default:
                        goto fix;
                }
        }

fix:
        fclose(fp);
        no = st.st_size - o;
        syslog(LOG_INFO, "%zu packets read from `%s', %zu extra bytes",
            count, ctx->path, no);
        if (no < 10240) {
                syslog(LOG_WARNING,
                    "Incomplete last packet in `%s', truncating",
                    ctx->path);
                if (truncate(ctx->path, (off_t)o) == -1) {
                        syslog(LOG_ERR, "Cannot truncate `%s': %m", ctx->path);
                        goto rename;
                }
        } else {
                syslog(LOG_ERR, "Corrupt file `%s'", ctx->path);
                goto rename;
        }
        fclose(fp);
        return hdr.snaplen;
rename:
        fclose(fp);
        char tmp[MAXPATHLEN];
        if (snprintf(tmp, sizeof(tmp), "%s.XXXXXX", ctx->path) > MAXPATHLEN)
                syslog(LOG_ERR, "Temp file truncated: `%s' does not fit",
                       ctx->path);
        int fd;
        if ((fd = mkstemp(tmp)) == -1) {
                syslog(LOG_ERR, "Can't make temp file `%s': %m", tmp);
                return -1;
        }
        close(fd);
        if (rename(ctx->path, tmp) == -1) {
                syslog(LOG_ERR, "Can't rename `%s' to `%s': %m",
                    ctx->path, tmp);
                return -1;
        }
        syslog(LOG_ERR, "Renamed to `%s'", tmp);
        return 0;
}
        

npfd_log_t *
npfd_log_create(const char *filename, const char *ifname, const char *filter,
    int snaplen)
{
        npfd_log_t *ctx;

        if ((ctx = calloc(1, sizeof(*ctx))) == NULL)
                err(EXIT_FAILURE, "malloc failed");

        snprintf(ctx->ifname, sizeof(ctx->ifname), "%s", ifname);
        if (filename == NULL)
                snprintf(ctx->path, sizeof(ctx->path), NPFD_LOG_PATH "/%s.pcap",
                    ctx->ifname);
        else
                snprintf(ctx->path, sizeof(ctx->path), "%s", filename);

        if (filter != NULL) {
                ctx->filter = strdup(filter);
                if (ctx->filter == NULL)
                        err(EXIT_FAILURE, "malloc failed");
        }
        ctx->snaplen = snaplen;

        /* Open a live capture handle in non-blocking mode.  */
        npfd_log_pcap_reopen(ctx);

        /* Open the log file */
        npfd_log_file_reopen(ctx, false);
        return ctx;
}


bool
npfd_log_pcap_reopen(npfd_log_t *ctx)
{
        char errbuf[PCAP_ERRBUF_SIZE];
        int snaplen = ctx->snaplen;
        int rc;

        if (ctx->pcap != NULL)
                pcap_close(ctx->pcap);
        else
                syslog(LOG_INFO, "reopening pcap socket");

        ctx->pcap = pcap_create(ctx->ifname, errbuf);
        if (ctx->pcap == NULL)
                errx(EXIT_FAILURE, "pcap_create failed: %s", errbuf);

        if (pcap_setnonblock(ctx->pcap, 1, errbuf) == -1)
                errx(EXIT_FAILURE, "pcap_setnonblock failed: %s", errbuf);

        int sl = npfd_log_getsnaplen(ctx);
        if (sl == -1)
                errx(EXIT_FAILURE, "corrupt log file `%s'", ctx->path);

        if (sl != 0 && sl != snaplen) {
                warnx("Overriding snaplen from %d to %d from `%s'", snaplen,
                    sl, ctx->path);
                snaplen = sl;
        }

        if (pcap_set_snaplen(ctx->pcap, snaplen) == -1)
                errx(EXIT_FAILURE, "pcap_set_snaplen failed: %s",
                    pcap_geterr(ctx->pcap));

        if (pcap_set_timeout(ctx->pcap, 1000) == -1)
                errx(EXIT_FAILURE, "pcap_set_timeout failed: %s",
                    pcap_geterr(ctx->pcap));

        if ((rc = pcap_activate(ctx->pcap)) != 0) {
                const char *msg = pcap_geterr(ctx->pcap);
                if (rc > 0) {
                        warnx("pcap_activate warning: %s", msg);
                } else {
                        errx(EXIT_FAILURE, "pcap_activate failed: %s", msg);
                }
        }

        npfd_log_setfilter(ctx);
        return true;
}

bool
npfd_log_file_reopen(npfd_log_t *ctx, bool die)
{
        mode_t omask = umask(077);

        if (ctx->dumper)
                pcap_dump_close(ctx->dumper);
        /*
         * Open a log file to write for a given interface and dump there.
         */
        switch (npfd_log_validate(ctx)) {
        case -1:
                syslog(LOG_ERR, "Giving up");
                exit(EXIT_FAILURE);
                /*NOTREACHED*/
        case 0:
                ctx->dumper = pcap_dump_open(ctx->pcap, ctx->path);
                break;
        default:
                ctx->dumper = pcap_dump_open_append(ctx->pcap, ctx->path);
                break;
        }
        (void)umask(omask);

        if (ctx->dumper == NULL) {
                if (die)
                        errx(EXIT_FAILURE, "pcap_dump_open failed for `%s': %s",
                            ctx->path, pcap_geterr(ctx->pcap));
                syslog(LOG_ERR, "pcap_dump_open failed for `%s': %s",
                    ctx->path, pcap_geterr(ctx->pcap));
                return false;
        }
        return true;
}

void
npfd_log_destroy(npfd_log_t *ctx)
{
        if (ctx->dumper)
                pcap_dump_close(ctx->dumper);
        if (ctx->pcap)
                pcap_close(ctx->pcap);
        free(ctx);
}

int
npfd_log_getsock(npfd_log_t *ctx)
{
        return pcap_get_selectable_fd(ctx->pcap);
}

void
npfd_log_flush(npfd_log_t *ctx)
{
        if (!ctx->dumper)
                return;
        if (pcap_dump_flush(ctx->dumper) == -1)
                syslog(LOG_ERR, "pcap_dump_flush failed for `%s': %m",
                    ctx->path);
}


int
npfd_log(npfd_log_t *ctx)
{
        pcap_dumper_t *dumper = ctx->dumper;

        return pcap_dispatch(ctx->pcap, PCAP_NPACKETS, pcap_dump,
            (void *)dumper);
}

void
npfd_log_stats(npfd_log_t *ctx)
{
        pcap_t *pcap = ctx->pcap;
        struct pcap_stat ps;

        if (pcap_stats(pcap, &ps) == -1) {
                syslog(LOG_ERR, "pcap_stats failed: %s", pcap_geterr(pcap));
                return;
        }
        syslog(LOG_INFO, "packet statistics: %s: %u received, %u dropped",
            ctx->ifname, ps.ps_recv, ps.ps_drop);
}