Function ng_pred1_compress

freebsd/netgraph/ng_pred1.c:381–458

* Compress/encrypt a packet and put the result in a new mbuf at *resultp. * The original mbuf is not free'd. */

 * The original mbuf is not free'd.
 */
static int
ng_pred1_compress(node_p node, struct mbuf *m, struct mbuf **resultp)
{
	const priv_p 	priv = NG_NODE_PRIVATE(node);
	int 		outlen, inlen;
	u_char		*out;
	uint16_t	fcs, lenn;
	int		len;

	/* Initialize. */
	*resultp = NULL;

	inlen = m->m_pkthdr.len;

	priv->stats.FramesPlain++;
	priv->stats.InOctets += inlen;

	/* Reserve space for expansion. */
	if (inlen > (PRED1_BUF_SIZE*8/9 + 1 + 4)) {
		priv->stats.Errors++;
		NG_FREE_M(m);
		return (ENOMEM);
	}

	/* We must own the mbuf chain exclusively to modify it. */
	m = m_unshare(m, M_NOWAIT);
	if (m == NULL) {
		priv->stats.Errors++;
		return (ENOMEM);
	}

	/* Work with contiguous regions of memory. */
	m_copydata(m, 0, inlen, (caddr_t)(priv->inbuf + 2));

	lenn = htons(inlen & 0x7FFF);

	/* Compute FCS. */
	fcs = Crc16(PPP_INITFCS, (u_char *)&lenn, 2);
	fcs = Crc16(fcs, priv->inbuf + 2, inlen);
	fcs = ~fcs;

	/* Compress data. */
	len = Pred1Compress(node, priv->inbuf + 2, priv->outbuf + 2, inlen);

	/* What happened? */
	if (len < inlen) {
		out = priv->outbuf;
		outlen = 2 + len;
		*(uint16_t *)out = lenn;
		*out |= 0x80;
		priv->stats.FramesComp++;
	} else {
		out = priv->inbuf;
		outlen = 2 + inlen;
		*(uint16_t *)out = lenn;
		priv->stats.FramesUncomp++;
	}