static int ipv6cp_nakci()

in net/ip/lwip_base/src/netif/ppp/ipv6cp.c [671:800]

• 100 lines of code
• 31 McCabe index (conditional complexity)

static int ipv6cp_nakci(fsm *f, u_char *p, int len, int treat_as_reject) {
    ppp_pcb *pcb = f->pcb;
    ipv6cp_options *go = &pcb->ipv6cp_gotoptions;
    u_char citype, cilen, *next;
#ifdef IPV6CP_COMP
    u_short cishort;
#endif /* IPV6CP_COMP */
    eui64_t ifaceid;
    ipv6cp_options no;		/* options we've seen Naks for */
    ipv6cp_options try_;	/* options to request next time */

    BZERO(&no, sizeof(no));
    try_ = *go;

    /*
     * Any Nak'd CIs must be in exactly the same order that we sent.
     * Check packet length and CI length at each step.
     * If we find any deviations, then this packet is bad.
     */
#define NAKCIIFACEID(opt, neg, code) \
    if (go->neg && \
	len >= (cilen = CILEN_IFACEID) && \
	p[1] == cilen && \
	p[0] == opt) { \
	len -= cilen; \
	INCPTR(2, p); \
	eui64_get(ifaceid, p); \
	no.neg = 1; \
	code \
    }

#ifdef IPV6CP_COMP
#define NAKCIVJ(opt, neg, code) \
    if (go->neg && \
	((cilen = p[1]) == CILEN_COMPRESS) && \
	len >= cilen && \
	p[0] == opt) { \
	len -= cilen; \
	INCPTR(2, p); \
	GETSHORT(cishort, p); \
	no.neg = 1; \
        code \
    }
#endif /* IPV6CP_COMP */

    /*
     * Accept the peer's idea of {our,his} interface identifier, if different
     * from our idea, only if the accept_{local,remote} flag is set.
     */
    NAKCIIFACEID(CI_IFACEID, neg_ifaceid,
		 if (treat_as_reject) {
		     try_.neg_ifaceid = 0;
		 } else if (go->accept_local) {
		     while (eui64_iszero(ifaceid) || 
			    eui64_equals(ifaceid, go->hisid)) /* bad luck */
			 eui64_magic(ifaceid);
		     try_.ourid = ifaceid;
		     IPV6CPDEBUG(("local LL address %s", llv6_ntoa(ifaceid)));
		 }
		 );

#ifdef IPV6CP_COMP
    NAKCIVJ(CI_COMPRESSTYPE, neg_vj,
	    {
		if (cishort == IPV6CP_COMP && !treat_as_reject) {
		    try_.vj_protocol = cishort;
		} else {
		    try_.neg_vj = 0;
		}
	    }
	    );
#endif /* IPV6CP_COMP */

    /*
     * There may be remaining CIs, if the peer is requesting negotiation
     * on an option that we didn't include in our request packet.
     * If they want to negotiate about interface identifier, we comply.
     * If they want us to ask for compression, we refuse.
     */
    while (len >= CILEN_VOID) {
	GETCHAR(citype, p);
	GETCHAR(cilen, p);
	if ( cilen < CILEN_VOID || (len -= cilen) < 0 )
	    goto bad;
	next = p + cilen - 2;

	switch (citype) {
#ifdef IPV6CP_COMP
	case CI_COMPRESSTYPE:
	    if (go->neg_vj || no.neg_vj ||
		(cilen != CILEN_COMPRESS))
		goto bad;
	    no.neg_vj = 1;
	    break;
#endif /* IPV6CP_COMP */
	case CI_IFACEID:
	    if (go->neg_ifaceid || no.neg_ifaceid || cilen != CILEN_IFACEID)
		goto bad;
	    try_.neg_ifaceid = 1;
	    eui64_get(ifaceid, p);
	    if (go->accept_local) {
		while (eui64_iszero(ifaceid) || 
		       eui64_equals(ifaceid, go->hisid)) /* bad luck */
		    eui64_magic(ifaceid);
		try_.ourid = ifaceid;
	    }
	    no.neg_ifaceid = 1;
	    break;
	default:
	    break;
	}
	p = next;
    }

    /* If there is still anything left, this packet is bad. */
    if (len != 0)
	goto bad;

    /*
     * OK, the Nak is good.  Now we can update state.
     */
    if (f->state != PPP_FSM_OPENED)
	*go = try_;

    return 1;

bad:
    IPV6CPDEBUG(("ipv6cp_nakci: received bad Nak!"));
    return 0;
}