savefile.c

用来监视网络通信数据的源代码和应用程序,方便网络程序底层开发.

	hdr.thiszone = thiszone;
	hdr.snaplen = snaplen;
	hdr.sigfigs = 0;
	hdr.linktype = linktype;

	if (fwrite((char *)&hdr, sizeof(hdr), 1, fp) != 1)
		return (-1);

	return (0);
}

static void
swap_hdr(struct pcap_file_header *hp)
{
	hp->version_major = SWAPSHORT(hp->version_major);
	hp->version_minor = SWAPSHORT(hp->version_minor);
	hp->thiszone = SWAPLONG(hp->thiszone);
	hp->sigfigs = SWAPLONG(hp->sigfigs);
	hp->snaplen = SWAPLONG(hp->snaplen);
	hp->linktype = SWAPLONG(hp->linktype);
}

pcap_t *
pcap_open_offline(const char *fname, char *errbuf)
{
	register pcap_t *p;
	register FILE *fp;
	struct pcap_file_header hdr;
	bpf_u_int32 magic;
	int linklen;

	p = (pcap_t *)malloc(sizeof(*p));
	if (p == NULL) {
		strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
		return (NULL);
	}

	memset((char *)p, 0, sizeof(*p));
	/*
	 * Set this field so we don't close stdin in pcap_close!
	 */
#ifndef WIN32
	p->fd = -1;
#else
	p->adapter = NULL;
#endif

	if (fname[0] == '-' && fname[1] == '\0')
		fp = stdin;
	else {
#ifndef WIN32
		fp = fopen(fname, "r");
#else
		fp = fopen(fname, "rb");
#endif
		if (fp == NULL) {
			snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", fname,
			    pcap_strerror(errno));
			goto bad;
		}
	}
	if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) {
		snprintf(errbuf, PCAP_ERRBUF_SIZE, "fread: %s",
		    pcap_strerror(errno));
		goto bad;
	}
	magic = hdr.magic;
	if (magic != TCPDUMP_MAGIC && magic != PATCHED_TCPDUMP_MAGIC) {
		magic = SWAPLONG(magic);
		if (magic != TCPDUMP_MAGIC && magic != PATCHED_TCPDUMP_MAGIC) {
			snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "bad dump file format");
			goto bad;
		}
		p->sf.swapped = 1;
		swap_hdr(&hdr);
	}
	if (magic == PATCHED_TCPDUMP_MAGIC) {
		/*
		 * XXX - the patch that's in some versions of libpcap
		 * changes the packet header but not the magic number;
		 * we'd have to use some hacks^H^H^H^H^Hheuristics to
		 * detect that.
		 */
		p->sf.hdrsize = sizeof(struct pcap_sf_patched_pkthdr);
	} else
		p->sf.hdrsize = sizeof(struct pcap_sf_pkthdr);
	if (hdr.version_major < PCAP_VERSION_MAJOR) {
		snprintf(errbuf, PCAP_ERRBUF_SIZE, "archaic file format");
		goto bad;
	}
	p->tzoff = hdr.thiszone;
	p->snapshot = hdr.snaplen;
	p->linktype = linktype_to_dlt(hdr.linktype);
	p->sf.rfile = fp;
#ifndef WIN32
	p->bufsize = hdr.snaplen;
#else
	/* Allocate the space for pcap_pkthdr as well. It will be used by pcap_read_ex */
	p->bufsize = hdr.snaplen+sizeof(struct pcap_pkthdr);
#endif

	/* Align link header as required for proper data alignment */
	/* XXX should handle all types */
	switch (p->linktype) {

	case DLT_EN10MB:
		linklen = 14;
		break;

	case DLT_FDDI:
		linklen = 13 + 8;	/* fddi_header + llc */
		break;

	case DLT_NULL:
	default:
		linklen = 0;
		break;
	}

	if (p->bufsize < 0)
		p->bufsize = BPF_MAXBUFSIZE;
	p->sf.base = (u_char *)malloc(p->bufsize + BPF_ALIGNMENT);
	if (p->sf.base == NULL) {
		strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
		goto bad;
	}
	p->buffer = p->sf.base + BPF_ALIGNMENT - (linklen % BPF_ALIGNMENT);
	p->sf.version_major = hdr.version_major;
	p->sf.version_minor = hdr.version_minor;
#ifdef PCAP_FDDIPAD
	/* XXX padding only needed for kernel fcode */
	pcap_fddipad = 0;
#endif

	return (p);
 bad:
	if(fp)
		fclose(fp);
	free(p);
	return (NULL);
}

/*
 * Read sf_readfile and return the next packet.  Return the header in hdr
 * and the contents in buf.  Return 0 on success, SFERR_EOF if there were
 * no more packets, and SFERR_TRUNC if a partial packet was encountered.
 */
#if (defined(HAVE_PCAPREADEX) || defined(WIN32) )
int
#else
static int
#endif
sf_next_packet(pcap_t *p, struct pcap_pkthdr *hdr, u_char *buf, int buflen)
{
	struct pcap_sf_patched_pkthdr sf_hdr;
	FILE *fp = p->sf.rfile;

	/*
	 * Read the packet header; the structure we use as a buffer
	 * is the longer structure for files generated by the patched
	 * libpcap, but if the file has the magic number for an
	 * unpatched libpcap we only read as many bytes as the regular
	 * header has.
	 */
	if (fread(&sf_hdr, p->sf.hdrsize, 1, fp) != 1) {
		/* probably an EOF, though could be a truncated packet */
		return (1);
	}

	if (p->sf.swapped) {
		/* these were written in opposite byte order */
		hdr->caplen = SWAPLONG(sf_hdr.caplen);
		hdr->len = SWAPLONG(sf_hdr.len);
		hdr->ts.tv_sec = SWAPLONG(sf_hdr.ts.tv_sec);
		hdr->ts.tv_usec = SWAPLONG(sf_hdr.ts.tv_usec);
	} else {
		hdr->caplen = sf_hdr.caplen;
		hdr->len = sf_hdr.len;
		hdr->ts.tv_sec = sf_hdr.ts.tv_sec;
		hdr->ts.tv_usec = sf_hdr.ts.tv_usec;
	}
	/*
	 * We interchanged the caplen and len fields at version 2.3,
	 * in order to match the bpf header layout.  But unfortunately
	 * some files were written with version 2.3 in their headers
	 * but without the interchanged fields.
	 */
	if (p->sf.version_minor < 3 ||
	    (p->sf.version_minor == 3 && hdr->caplen > hdr->len)) {
		int t = hdr->caplen;
		hdr->caplen = hdr->len;
		hdr->len = t;
	}

	if (hdr->caplen > buflen) {
		/*
		 * This can happen due to Solaris 2.3 systems tripping
		 * over the BUFMOD problem and not setting the snapshot
		 * correctly in the savefile header.  If the caplen isn't
		 * grossly wrong, try to salvage.
		 */
		static u_char *tp = NULL;
		static int tsize = 0;

		if (hdr->caplen > 65535) {
			snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
			    "bogus savefile header");
			return (-1);
		}

		if (tsize < hdr->caplen) {
			tsize = ((hdr->caplen + 1023) / 1024) * 1024;
			if (tp != NULL)
				free((u_char *)tp);
			tp = (u_char *)malloc(tsize);
			if (tp == NULL) {
				tsize = 0;
				snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
				    "BUFMOD hack malloc");
				return (-1);
			}
		}
		if (fread((char *)tp, hdr->caplen, 1, fp) != 1) {
			snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
			    "truncated dump file");
			return (-1);
		}
		/*
		 * We can only keep up to buflen bytes.  Since caplen > buflen
		 * is exactly how we got here, we know we can only keep the
		 * first buflen bytes and must drop the remainder.  Adjust
		 * caplen accordingly, so we don't get confused later as
		 * to how many bytes we have to play with.
		 */
		hdr->caplen = buflen;
		memcpy((char *)buf, (char *)tp, buflen);

	} else {
		/* read the packet itself */

		if (fread((char *)buf, hdr->caplen, 1, fp) != 1) {
			snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
			    "truncated dump file");
			return (-1);
		}
	}
	return (0);
}

/*
 * Print out packets stored in the file initialized by sf_read_init().
 * If cnt > 0, return after 'cnt' packets, otherwise continue until eof.
 */
int
pcap_offline_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
	struct bpf_insn *fcode = p->fcode.bf_insns;
	int status = 0;
	int n = 0;

	while (status == 0) {
		struct pcap_pkthdr h;

		status = sf_next_packet(p, &h, p->buffer, p->bufsize);
		if (status) {
			if (status == 1)
				return (0);
			return (status);
		}

		if (fcode == NULL ||
		    bpf_filter(fcode, p->buffer, h.len, h.caplen)) {
			(*callback)(user, &h, p->buffer);
			if (++n >= cnt && cnt > 0)
				break;
		}
	}
	/*XXX this breaks semantics tcpslice expects */
	return (n);
}

/*
 * Output a packet to the initialized dump file.
 */
void
pcap_dump(u_char *user, const struct pcap_pkthdr *h, const u_char *sp)
{
	register FILE *f;
	struct pcap_sf_pkthdr sf_hdr;

	f = (FILE *)user;
	sf_hdr.ts.tv_sec  = h->ts.tv_sec;
	sf_hdr.ts.tv_usec = h->ts.tv_usec;
	sf_hdr.caplen     = h->caplen;
	sf_hdr.len        = h->len;
	/* XXX we should check the return status */
	(void)fwrite(&sf_hdr, sizeof(sf_hdr), 1, f);
	(void)fwrite((char *)sp, h->caplen, 1, f);
}

/*
 * Initialize so that sf_write() will output to the file named 'fname'.
 */
pcap_dumper_t *
pcap_dump_open(pcap_t *p, const char *fname)
{
	FILE *f;
	int linktype;

	linktype = dlt_to_linktype(p->linktype);
	if (linktype == -1) {
		snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
		    "%s: link-layer type %d isn't supported in savefiles",
		    fname, linktype);
		return (NULL);
	}

	if (fname[0] == '-' && fname[1] == '\0') {
		f = stdout;
#ifdef WIN32
		_setmode(_fileno(f), _O_BINARY);
#endif
	} else {
#ifndef WIN32
		f = fopen(fname, "w");
#else
		f = fopen(fname, "wb");
		setbuf(f, NULL);	/* XXX - why? */
#endif
		if (f == NULL) {
			snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "%s: %s",
			    fname, pcap_strerror(errno));
			return (NULL);
		}
	}
	(void)sf_write_header(f, linktype, p->tzoff, p->snapshot);
	return ((pcap_dumper_t *)f);
}

int
pcap_dump_flush(pcap_dumper_t *p)
{

	if (fflush((FILE *)p) == EOF)
		return (-1);
	else
		return (0);
}

void
pcap_dump_close(pcap_dumper_t *p)
{

#ifdef notyet
	if (ferror((FILE *)p))
		return-an-error;
	/* XXX should check return from fclose() too */
#endif
	(void)fclose((FILE *)p);
}