Function AliasHandlePptpOut

freebsd/netinet/libalias/alias_pptp.c:298–368

static PptpCallId AliasVerifyPptp(struct ip *, u_int16_t *);

static void
AliasHandlePptpOut(struct libalias *la,
    struct ip *pip,		/* IP packet to examine/patch */
    struct alias_link *lnk)
{				/* The PPTP control link */
	struct alias_link *pptp_lnk;
	PptpCallId cptr;
	PptpCode codes;
	u_int16_t ctl_type;	/* control message type */
	struct tcphdr *tc;

	/* Verify valid PPTP control message */
	if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL)
		return;

	/* Modify certain PPTP messages */
	switch (ctl_type) {
	case PPTP_OutCallRequest:
	case PPTP_OutCallReply:
	case PPTP_InCallRequest:
	case PPTP_InCallReply:
		/*
		 * Establish PPTP link for address and Call ID found in
		 * control message.
		 */
		pptp_lnk = AddPptp(la, GetOriginalAddress(lnk), GetDestAddress(lnk),
		    GetAliasAddress(lnk), cptr->cid1);
		break;
	case PPTP_CallClearRequest:
	case PPTP_CallDiscNotify:
		/*
		 * Find PPTP link for address and Call ID found in control
		 * message.
		 */
		pptp_lnk = FindPptpOutByCallId(la, GetOriginalAddress(lnk),
		    GetDestAddress(lnk),
		    cptr->cid1);
		break;
	default:
		return;
	}

	if (pptp_lnk != NULL) {
		int accumulate = cptr->cid1;

		/* alias the Call Id */
		cptr->cid1 = GetAliasPort(pptp_lnk);

		/* Compute TCP checksum for revised packet */
		tc = (struct tcphdr *)ip_next(pip);
		accumulate -= cptr->cid1;
		ADJUST_CHECKSUM(accumulate, tc->th_sum);

		switch (ctl_type) {
		case PPTP_OutCallReply:
		case PPTP_InCallReply:
			codes = (PptpCode) (cptr + 1);
			if (codes->resCode == 1)	/* Connection