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Link ALTQ to the build and break with ABI for struct ifnet. Please recompile

Browse Source 
your (network) modules as well as any userland that might make sense of
sizeof(struct ifnet).
This does not change the queueing yet. These changes will follow in a
seperate commit. Same with the driver changes, which need case by case
evaluation.

__FreeBSD_version bump will follow.

Tested-by:	(i386)LINT
This commit is contained in:
mlaier 2004-06-13 17:29:10 +00:00
parent 469e445f95
commit 977d97b004
20 changed files with 302 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
etc/mtree/BSD.include.dist
View File

@ -5,6 +5,8 @@
/set type=dir uname=root gname=wheel mode=0755
.
altq
..
arpa
..
bsnmp

8
include/Makefile
View File

@ -111,6 +111,9 @@ copies:
cd ${.CURDIR}/../sys/dev/bktr; \
${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 ioctl_*.h \
${DESTDIR}${INCLUDEDIR}/dev/bktr
cd ${.CURDIR}/../sys/contrib/altq/altq; \
${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 *.h \
${DESTDIR}${INCLUDEDIR}/altq
cd ${.CURDIR}/../sys/contrib/ipfilter/netinet; \
${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 *.h \
${DESTDIR}${INCLUDEDIR}/netinet
@ -149,6 +152,11 @@ symlinks:
ln -fs ../../../../../sys/$i/$$h ${DESTDIR}${INCLUDEDIR}/$i; \
done
.endfor
cd ${.CURDIR}/../sys/contrib/altq/altq; \
for h in *.h; do \
ln -fs ../../../sys/contrib/altq/altq/$$h \
${DESTDIR}${INCLUDEDIR}/altq; \
done
cd ${.CURDIR}/../sys/contrib/ipfilter/netinet; \
for h in *.h; do \
ln -fs ../../../sys/contrib/ipfilter/netinet/$$h \

14
sys/conf/NOTES
View File

@ -399,6 +399,20 @@ options NETSMBCRYPTO #encrypted password support for SMB
# mchain library. It can be either loaded as KLD or compiled into kernel
options LIBMCHAIN
# altq(9). Enable the base part of the hooks with the ALTQ option.
# Individual disciplines must be built into the base system and can not be
# loaded as modules at this point. In order to build a SMP kernel you must
# also have the ALTQ_NOPCC option.
options ALTQ
options ALTQ_CBQ # Class Bases Queueing
options ALTQ_RED # Random Early Drop
options ALTQ_RIO # RED In/Out
options ALTQ_HFSC # Hierarchical Packet Scheduler
options ALTQ_CDNR # Traffic conditioner
options ALTQ_PRIQ # Prioirity Queueing
options ALTQ_NOPCC # Required for SMP build
options ALTQ_DEBUG
# netgraph(4). Enable the base netgraph code with the NETGRAPH option.
# Individual node types can be enabled with the corresponding option
# listed below; however, this is not strictly necessary as netgraph

8
sys/conf/files
View File

@ -85,6 +85,14 @@ coda/coda_venus.c optional vcoda
coda/coda_vfsops.c optional vcoda
coda/coda_vnops.c optional vcoda
compat/linprocfs/linprocfs.c optional linprocfs
contrib/altq/altq/altq_cbq.c optional altq
contrib/altq/altq/altq_cdnr.c optional altq
contrib/altq/altq/altq_hfsc.c optional altq
contrib/altq/altq/altq_priq.c optional altq
contrib/altq/altq/altq_red.c optional altq
contrib/altq/altq/altq_rio.c optional altq
contrib/altq/altq/altq_rmclass.c optional altq
contrib/altq/altq/altq_subr.c optional altq
contrib/dev/acpica/dbcmds.c optional acpi acpi_debug
contrib/dev/acpica/dbdisply.c optional acpi acpi_debug
contrib/dev/acpica/dbexec.c optional acpi acpi_debug

3
sys/conf/kern.pre.mk
View File

@ -51,6 +51,9 @@ INCLUDES= ${NOSTDINC} -I- ${INCLMAGIC} -I. -I$S
# include path into 100+ source files.
INCLUDES+= -I$S/contrib/dev/acpica
# ... and the same for altq
INCLUDES+= -I$S/contrib/altq
# ... and the same for ipfilter
INCLUDES+= -I$S/contrib/ipfilter

4
sys/conf/kmod.mk
View File

@ -96,6 +96,10 @@ CFLAGS+= -include ${KERNBUILDDIR}/opt_global.h
# set because there are no standard paths for non-headers.
CFLAGS+= -I. -I@
# Add -I path for altq headers as they are included via net/if_var.h
# for example.
CFLAGS+= -I@/contrib/altq
# Add a -I path to standard headers like <stddef.h>. Use a relative
# path to src/include if possible. If the @ symlink hasn't been built
# yet, then we can't tell if the relative path exists. Add both the

9
sys/conf/options
View File

@ -294,6 +294,15 @@ DEV_ATARAID opt_ata.h
# Net stuff.
ACCEPT_FILTER_DATA
ACCEPT_FILTER_HTTP
ALTQ opt_global.h
ALTQ_CBQ opt_altq.h
ALTQ_RED opt_altq.h
ALTQ_RIO opt_altq.h
ALTQ_HFSC opt_altq.h
ALTQ_CDNR opt_altq.h
ALTQ_PRIQ opt_altq.h
ALTQ_NOPCC opt_altq.h
ALTQ_DEBUG opt_altq.h
BOOTP opt_bootp.h
BOOTP_COMPAT opt_bootp.h
BOOTP_NFSROOT opt_bootp.h

2
sys/dev/awi/awi.c
View File

@ -235,10 +235,12 @@ ether_sprintf(u_int8_t *enaddr)
}
#endif
#if 0 /* ALTQ */
#define IFQ_PURGE(ifq) IF_DRAIN(ifq)
#define IF_POLL(ifq, m) ((m) = (ifq)->ifq_head)
#define IFQ_POLL(ifq, m) IF_POLL((ifq), (m))
#define IFQ_DEQUEUE(ifq, m) IF_DEQUEUE((ifq), (m))
#endif
#endif

2
sys/dev/pdq/pdq_freebsd.h
View File

@ -97,8 +97,10 @@ enum _pdq_type_t {
#define sc_ifmedia ifmedia
#define sc_if arpcom.ac_if
#define sc_bpf sc_if.if_bpf
#if 0 /* ALTQ */
#define IFQ_DEQUEUE IF_DEQUEUE
#define IFQ_IS_EMPTY(q) ((q)->ifq_len == 0)
#endif
typedef struct _pdq_os_ctx_t {
struct arpcom arpcom;

2
sys/dev/wi/if_wi.c
View File

@ -114,9 +114,11 @@ __FBSDID("$FreeBSD$");
#include <dev/wi/if_wireg.h>
#include <dev/wi/if_wivar.h>
#if 0 /* ALTQ */
#define IF_POLL(ifq, m) ((m) = (ifq)->ifq_head)
#define IFQ_POLL(ifq, m) IF_POLL((ifq), (m))
#define IFQ_DEQUEUE(ifq, m) IF_DEQUEUE((ifq), (m))
#endif
static void wi_start(struct ifnet *);
static int wi_reset(struct wi_softc *);

2
sys/i4b/driver/i4b_ipr.c
View File

@ -382,7 +382,7 @@ i4biproutput(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
if(ip->ip_tos & IPTOS_LOWDELAY)
ifq = &sc->sc_fastq;
else
ifq = &sc->sc_if.if_snd;
ifq = (struct ifqueue *)&sc->sc_if.if_snd;
/* check for space in choosen send queue */

21
sys/net/if.c
View File

@ -82,7 +82,7 @@ static void if_grow(void);
static void if_init(void *);
static void if_check(void *);
static int if_findindex(struct ifnet *);
static void if_qflush(struct ifqueue *);
static void if_qflush(struct ifaltq *);
static void if_route(struct ifnet *, int flag, int fam);
static void if_slowtimo(void *);
static void if_unroute(struct ifnet *, int flag, int fam);
@ -441,6 +441,13 @@ if_attach(struct ifnet *ifp)
ifa->ifa_refcnt = 1;
TAILQ_INSERT_HEAD(&ifp->if_addrhead, ifa, ifa_link);
ifp->if_broadcastaddr = 0; /* reliably crash if used uninitialized */
#ifdef ALTQ
ifp->if_snd.altq_type = 0;
ifp->if_snd.altq_disc = NULL;
ifp->if_snd.altq_flags &= ALTQF_CANTCHANGE;
ifp->if_snd.altq_tbr = NULL;
ifp->if_snd.altq_ifp = ifp;
#endif
if (domains)
if_attachdomain1(ifp);
@ -519,6 +526,12 @@ if_detach(struct ifnet *ifp)
*/
s = splnet();
if_down(ifp);
#ifdef ALTQ
if (ALTQ_IS_ENABLED(&ifp->if_snd))
altq_disable(&ifp->if_snd);
if (ALTQ_IS_ATTACHED(&ifp->if_snd))
altq_detach(&ifp->if_snd);
#endif
for (ifa = TAILQ_FIRST(&ifp->if_addrhead); ifa; ifa = next) {
next = TAILQ_NEXT(ifa, ifa_link);
@ -1189,10 +1202,14 @@ if_up(struct ifnet *ifp)
* Flush an interface queue.
*/
static void
if_qflush(struct ifqueue *ifq)
if_qflush(struct ifaltq *ifq)
{
struct mbuf *m, *n;
#ifdef ALTQ
if (ALTQ_IS_ENABLED(ifq))
ALTQ_PURGE(ifq);
#endif
n = ifq->ifq_head;
while ((m = n) != 0) {
n = m->m_act;

6
sys/net/if_ppp.c
View File

@ -933,7 +933,8 @@ pppoutput(ifp, m0, dst, rtp)
sc->sc_npqtail = &m0->m_nextpkt;
} else {
/* fastq and if_snd are emptied at spl[soft]net now */
ifq = (m0->m_flags & M_HIGHPRI)? &sc->sc_fastq: &ifp->if_snd;
ifq = (m0->m_flags & M_HIGHPRI)? &sc->sc_fastq:
(struct ifqueue *)&ifp->if_snd;
IF_LOCK(ifq);
if (_IF_QFULL(ifq) && dst->sa_family != AF_UNSPEC) {
_IF_DROP(ifq);
@ -988,7 +989,8 @@ ppp_requeue(sc)
*/
*mpp = m->m_nextpkt;
m->m_nextpkt = NULL;
ifq = (m->m_flags & M_HIGHPRI)? &sc->sc_fastq: &sc->sc_if.if_snd;
ifq = (m->m_flags & M_HIGHPRI)? &sc->sc_fastq:
(struct ifqueue *)&sc->sc_if.if_snd;
if (! IF_HANDOFF(ifq, m, NULL)) {
sc->sc_if.if_oerrors++;
sc->sc_stats.ppp_oerrors++;

2
sys/net/if_sl.c
View File

@ -571,7 +571,7 @@ sloutput(ifp, m, dst, rtp)
m_freem(m);
return (EHOSTUNREACH);
}
ifq = &sc->sc_if.if_snd;
ifq = (struct ifqueue *)&sc->sc_if.if_snd;
ip = mtod(m, struct ip *);
if (sc->sc_if.if_flags & SC_NOICMP && ip->ip_p == IPPROTO_ICMP) {
m_freem(m);

4
sys/net/if_spppsubr.c
View File

@ -781,7 +781,7 @@ sppp_output(struct ifnet *ifp, struct mbuf *m,
s = splimp();
}
ifq = &ifp->if_snd;
ifq = (struct ifqueue *)&ifp->if_snd;
#ifdef INET
if (dst->sa_family == AF_INET) {
/* XXX Check mbuf length here? */
@ -1038,7 +1038,7 @@ sppp_flush(struct ifnet *ifp)
{
struct sppp *sp = (struct sppp*) ifp;
sppp_qflush (&sp->pp_if.if_snd);
sppp_qflush ((struct ifqueue *)&sp->pp_if.if_snd);
sppp_qflush (&sp->pp_fastq);
sppp_qflush (&sp->pp_cpq);
}

207
sys/net/if_var.h
View File

@ -82,6 +82,10 @@ struct ether_header;
#define IF_DUNIT_NONE -1
#if 1 /* ALTQ */
#include <altq/if_altq.h>
#endif
TAILQ_HEAD(ifnethead, ifnet); /* we use TAILQs so that the order of */
TAILQ_HEAD(ifaddrhead, ifaddr); /* instantiation is preserved in the list */
TAILQ_HEAD(ifprefixhead, ifprefix);
@ -171,7 +175,11 @@ struct ifnet {
(void *);
int (*if_resolvemulti) /* validate/resolve multicast */
(struct ifnet *, struct sockaddr **, struct sockaddr *);
#if 1 /* ALTQ */
struct ifaltq if_snd; /* output queue (includes altq) */
#else
struct ifqueue if_snd; /* output queue */
#endif
const u_int8_t *if_broadcastaddr; /* linklevel broadcast bytestring */
struct lltable *lltables; /* list of L3-L2 resolution tables */
@ -228,6 +236,7 @@ typedef void if_init_f_t(void *);
*/
#define IF_LOCK(ifq) mtx_lock(&(ifq)->ifq_mtx)
#define IF_UNLOCK(ifq) mtx_unlock(&(ifq)->ifq_mtx)
#define IF_LOCK_ASSERT(ifq) mtx_assert(&(ifq)->ifq_mtx, MA_OWNED)
#define _IF_QFULL(ifq) ((ifq)->ifq_len >= (ifq)->ifq_maxlen)
#define _IF_DROP(ifq) ((ifq)->ifq_drops++)
#define _IF_QLEN(ifq) ((ifq)->ifq_len)
@ -278,18 +287,25 @@ typedef void if_init_f_t(void *);
IF_UNLOCK(ifq); \
} while (0)
#define IF_DRAIN(ifq) do { \
#define _IF_POLL(ifq, m) ((m) = (ifq)->ifq_head)
#define IF_POLL(ifq, m) _IF_POLL(ifq, m)
#define _IF_DRAIN(ifq) do { \
struct mbuf *m; \
IF_LOCK(ifq); \
for (;;) { \
_IF_DEQUEUE(ifq, m); \
if (m == NULL) \
break; \
m_freem(m); \
} \
IF_UNLOCK(ifq); \
} while (0)
#define IF_DRAIN(ifq) do { \
IF_LOCK(ifq); \
_IF_DRAIN(ifq); \
IF_UNLOCK(ifq); \
} while(0)
#ifdef _KERNEL
/* interface address change event */
typedef void (*ifaddr_event_handler_t)(void *, struct ifnet *);
@ -311,8 +327,10 @@ EVENTHANDLER_DECLARE(if_clone_event, if_clone_event_handler_t);
#define IF_AFDATA_UNLOCK(ifp) mtx_unlock(&(ifp)->if_afdata_mtx)
#define IF_AFDATA_DESTROY(ifp) mtx_destroy(&(ifp)->if_afdata_mtx)
#define IF_HANDOFF(ifq, m, ifp) if_handoff(ifq, m, ifp, 0)
#define IF_HANDOFF_ADJ(ifq, m, ifp, adj) if_handoff(ifq, m, ifp, adj)
#define IF_HANDOFF(ifq, m, ifp) \
if_handoff((struct ifqueue *)ifq, m, ifp, 0)
#define IF_HANDOFF_ADJ(ifq, m, ifp, adj) \
if_handoff((struct ifqueue *)ifq, m, ifp, adj)
static __inline int
if_handoff(struct ifqueue *ifq, struct mbuf *m, struct ifnet *ifp, int adjust)
@ -338,6 +356,185 @@ if_handoff(struct ifqueue *ifq, struct mbuf *m, struct ifnet *ifp, int adjust)
(*ifp->if_start)(ifp);
return (1);
}
#if 1 /* ALTQ */
#define IFQ_ENQUEUE(ifq, m, err) \
do { \
IF_LOCK(ifq); \
if (ALTQ_IS_ENABLED(ifq)) \
ALTQ_ENQUEUE(ifq, m, NULL, err); \
else { \
if (_IF_QFULL(ifq)) { \
m_freem(m); \
(err) = ENOBUFS; \
} else { \
_IF_ENQUEUE(ifq, m); \
(err) = 0; \
} \
} \
if (err) \
(ifq)->ifq_drops++; \
IF_UNLOCK(ifq); \
} while (0)
#define IFQ_DEQUEUE_NOLOCK(ifq, m) \
do { \
if (TBR_IS_ENABLED(ifq)) \
(m) = tbr_dequeue(ifq, ALTDQ_REMOVE); \
else if (ALTQ_IS_ENABLED(ifq)) \
ALTQ_DEQUEUE(ifq, m); \
else \
_IF_DEQUEUE(ifq, m); \
} while (0)
#define IFQ_DEQUEUE(ifq, m) \
do { \
IF_LOCK(ifq); \
IFQ_DEQUEUE_NOLOCK(ifq, m); \
IF_UNLOCK(ifq); \
} while (0)
#define IFQ_POLL_NOLOCK(ifq, m) \
do { \
if (TBR_IS_ENABLED(ifq)) \
(m) = tbr_dequeue(ifq, ALTDQ_POLL); \
else if (ALTQ_IS_ENABLED(ifq)) \
ALTQ_POLL(ifq, m); \
else \
_IF_POLL(ifq, m); \
} while (0)
#define IFQ_POLL(ifq, m) \
do { \
IF_LOCK(ifq); \
IFQ_POLL_NOLOCK(ifq, m); \
IF_UNLOCK(ifq); \
} while (0)
#define IFQ_PURGE_NOLOCK(ifq) \
do { \
if (ALTQ_IS_ENABLED(ifq)) { \
ALTQ_PURGE(ifq); \
} else \
_IF_DRAIN(ifq); \
} while (0)
#define IFQ_PURGE(ifq) \
do { \
IF_LOCK(ifq); \
IFQ_PURGE_NOLOCK(ifq); \
IF_UNLOCK(ifq); \
} while (0)
#define IFQ_SET_READY(ifq) \
do { ((ifq)->altq_flags |= ALTQF_READY); } while (0)
#else /* !ALTQ */
#define IFQ_ENQUEUE(ifq, m, err) \
do { \
IF_LOCK(ifq); \
if (_IF_QFULL(ifq)) { \
m_freem(m); \
(err) = ENOBUFS; \
} else { \
_IF_ENQUEUE(ifq, m); \
(err) = 0; \
} \
if (err) \
(ifq)->ifq_drops++; \
IF_UNLOCK(ifq); \
} while (0)
#define IFQ_DEQUEUE_NOLOCK(ifq, m) _IF_DEQUEUE(ifq, m)
#define IFQ_DEQUEUE(ifq, m) IF_DEQUEUE(ifq, m)
#define IFQ_POLL_NOLOCK(ifq, m) _IF_POLL(ifq, m)
#define IFQ_POLL(ifq, m) IF_POLL(ifq, m)
#define IFQ_PURGE_NOLOCK(ifq) _IF_DRAIN(ifq)
#define IFQ_PURGE(ifq) IF_DRAIN(ifq)
#define IFQ_SET_READY(ifq) /* nothing */
#endif /* !ALTQ */
#define IFQ_LOCK(ifq) IF_LOCK(ifq)
#define IFQ_UNLOCK(ifq) IF_UNLOCK(ifq)
#define IFQ_LOCK_ASSERT(ifq) IF_LOCK_ASSERT(ifq)
#define IFQ_IS_EMPTY(ifq) ((ifq)->ifq_len == 0)
#define IFQ_INC_LEN(ifq) ((ifq)->ifq_len++)
#define IFQ_DEC_LEN(ifq) (--(ifq)->ifq_len)
#define IFQ_INC_DROPS(ifq) ((ifq)->ifq_drops++)
#define IFQ_SET_MAXLEN(ifq, len) ((ifq)->ifq_maxlen = (len))
#define IFQ_HANDOFF_ADJ(ifp, m, adj, err) \
do { \
int len; \
short mflags; \
\
len = (m)->m_pkthdr.len; \
mflags = (m)->m_flags; \
IFQ_ENQUEUE(&(ifp)->if_snd, m, err); \
if ((err) == 0) { \
(ifp)->if_obytes += len + (adj); \
if (mflags & M_MCAST) \
(ifp)->if_omcasts++; \
if (((ifp)->if_flags & IFF_OACTIVE) == 0) \
(*(ifp)->if_start)(ifp); \
} \
} while (0)
#define IFQ_HANDOFF(ifp, m, err) \
IFQ_HANDOFF_ADJ(ifq, m, 0, err)
#define IFQ_DRV_DEQUEUE(ifq, m) \
do { \
(m) = (ifq)->ifq_drv_head; \
if (m) { \
if (((ifq)->ifq_drv_head = (m)->m_nextpkt) == NULL) \
(ifq)->ifq_drv_tail = NULL; \
(m)->m_nextpkt = NULL; \
(ifq)->ifq_drv_len--; \
} else { \
IFQ_LOCK(ifq); \
IFQ_DEQUEUE_NOLOCK(ifq, m); \
while ((ifq)->ifq_drv_len < (ifq)->ifq_drv_maxlen) { \
struct mbuf *m0; \
IFQ_DEQUEUE_NOLOCK(ifq, m0); \
if (m0 == NULL) \
break; \
m0->m_nextpkt = NULL; \
if ((ifq)->ifq_drv_tail == NULL) \
(ifq)->ifq_drv_head = m0; \
else \
(ifq)->ifq_drv_tail->m_nextpkt = m0; \
(ifq)->ifq_drv_tail = m0; \
(ifq)->ifq_drv_len++; \
} \
IFQ_UNLOCK(ifq); \
} \
} while (0)
#define IFQ_DRV_PREPEND(ifq, m) \
do { \
(m)->m_nextpkt = (ifq)->ifq_drv_head; \
if ((ifq)->ifq_tail == NULL) \
(ifq)->ifq_tail = (m); \
(ifq)->ifq_drv_head = (m); \
(ifq)->ifq_drv_len++; \
} while (0)
#define IFQ_DRV_IS_EMPTY(ifq) \
(((ifq)->ifq_drv_len == 0) && ((ifq)->ifq_len == 0))
#define IFQ_DRV_PURGE(ifq) \
do { \
struct mbuf *m = (ifq)->ifq_drv_head; \
while(m != NULL) { \
m = m->m_nextpkt; \
m_freem(m); \
} \
(ifq)->ifq_drv_head = (ifq)->ifq_drv_tail = NULL; \
(ifq)->ifq_drv_len = 0; \
IFQ_PURGE(ifq); \
} while (0)
/*
* 72 was chosen below because it is the size of a TCP/IP

5
sys/net80211/ieee80211_input.c
View File

@ -288,11 +288,6 @@ ieee80211_input(struct ifnet *ifp, struct mbuf *m, struct ieee80211_node *ni,
}
}
if (m1 != NULL) {
#ifdef ALTQ
if (ALTQ_IS_ENABLED(&ifp->if_snd))
altq_etherclassify(&ifp->if_snd, m1,
&pktattr);
#endif
len = m1->m_pkthdr.len;
IF_ENQUEUE(&ifp->if_snd, m1);
if (m != NULL)

6
sys/netinet/ip_input.c
View File

@ -390,6 +390,12 @@ ip_input(struct mbuf *m)
goto bad;
}
#ifdef ALTQ
if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0)
/* packet is dropped by traffic conditioner */
return;
#endif
/*
* Convert fields to host representation.
*/

7
sys/netinet/ip_output.c
View File

@ -404,6 +404,12 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
}
}
#endif /* notdef */
#ifdef ALTQ
/*
* disable packet drop hack.
* packetdrop should be done by queueing.
*/
#else /* !ALTQ */
/*
* Verify that we have any chance at all of being able to queue
* the packet or packet fragments
@ -414,6 +420,7 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro,
ipstat.ips_odropped++;
goto bad;
}
#endif /* !ALTQ */
/*
* Look for broadcast address and

6
sys/netinet6/ip6_input.c
View File

@ -366,6 +366,12 @@ ip6_input(m)
goto bad;
}
#ifdef ALTQ
if (altq_input != NULL && (*altq_input)(m, AF_INET6) == 0) {
/* packet is dropped by traffic conditioner */
return;
}
#endif
/*
* The following check is not documented in specs. A malicious
* party may be able to use IPv4 mapped addr to confuse tcp/udp stack