From: Alexander Bluhm Subject: Re: IP6_EXTHDR_GET pass mbuf pointer To: tech@openbsd.org Date: Sun, 25 May 2025 11:59:23 +0900 On Thu, May 22, 2025 at 05:23:48PM +0200, Claudio Jeker wrote: > On Fri, May 23, 2025 at 12:07:46AM +0900, Alexander Bluhm wrote: > > On Thu, May 22, 2025 at 04:25:57PM +0200, Claudio Jeker wrote: > > > Would it make sense to actually kill this macro and make it a proper > > > function? This thing is a monster and it probably makes things slower if > > > anything. > > > > I was considering this. Problem is that typ is passed. Then the > > return pointer is casted accordingly. Maybe we get can get away > > with void pointer and the compiler doing its job. > > (val) = (typ)(mtod((*(mp)), caddr_t) + (off)); \ > (val) = (typ)NULL; \ > > Urgh, these casts are just horrible. I think using a void * as return > works equally well. > > > static inline void *ip6_exthdr_get(struct mbuf **mp, int off, int len); > > th = ip6_exthdr_get(mp, iphlen, sizeof(*th)); > > Please use a size_t len argument. Also I'm not sure if you gain anything > from static inline. Would be an interesting experiment. Here is the ip6_exthdr_get() function diff. I make it static inline in netinet/ip6.h, mainly because we have no proper C file for it. There is no ip6.c. And it has to be in netinet as it is used by TCP and UDP in kernel without IPv6. Then the namespace ip6_ would be inconsistent. Keeping it in in6.h avoids all these naming problems. And the inline function is not very long. I moved the panic("m_pulldown malfunction") as kassert into m_pulldown(). Then it is only implemented once. The code is complicated enough that checking makes some sense. Regarding the type of len, I don't know. A lot of sizes in the network stack are passed around as signed int. At least that avoids type confusion when comparing them against each other. len is passed to m_pulldown() which also takes an int. The callers of ip6_exthdr_get() pass int or size_t to off or len inconsistently. I think it is best to keep everthing int as it is. I have also wrapped an ugly a long line in the diff's context. ok? bluhm Index: kern/uipc_mbuf2.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/kern/uipc_mbuf2.c,v diff -u -p -r1.47 uipc_mbuf2.c --- kern/uipc_mbuf2.c 29 Aug 2024 16:42:30 -0000 1.47 +++ kern/uipc_mbuf2.c 24 May 2025 14:02:05 -0000 @@ -213,6 +213,7 @@ m_pulldown(struct mbuf *m, int off, int off = 0; ok: + KASSERT(n->m_len >= off + len); if (offp) *offp = off; return (n); Index: netinet/ip6.h =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/ip6.h,v diff -u -p -r1.22 ip6.h --- netinet/ip6.h 24 May 2025 12:27:23 -0000 1.22 +++ netinet/ip6.h 24 May 2025 14:21:57 -0000 @@ -267,28 +267,27 @@ struct ip6_frag { #ifdef _KERNEL /* - * IP6_EXTHDR_GET ensures that intermediate protocol header (from "off" to - * "len") is located in single mbuf, on contiguous memory region. + * ip6_exthdr_get() ensures that intermediate protocol header (from "off" + * to "len") is located in single mbuf, on contiguous memory region. * The pointer to the region will be returned to pointer variable "val", * with type "typ". */ -#define IP6_EXTHDR_GET(val, typ, mp, off, len) \ -do { \ - struct mbuf *t; \ - int tmp; \ - if ((*(mp))->m_len >= (off) + (len)) \ - (val) = (typ)(mtod((*(mp)), caddr_t) + (off)); \ - else { \ - t = m_pulldown((*(mp)), (off), (len), &tmp); \ - if (t) { \ - if (t->m_len < tmp + (len)) \ - panic("m_pulldown malfunction"); \ - (val) = (typ)(mtod(t, caddr_t) + tmp); \ - } else { \ - (val) = (typ)NULL; \ - (*(mp)) = NULL; \ - } \ - } \ -} while (/* CONSTCOND */ 0) + +static inline void * +ip6_exthdr_get(struct mbuf **mp, int off, int len) +{ + struct mbuf *t; + int toff; + + if ((*mp)->m_len >= off + len) + return (mtod(*mp, caddr_t) + off); + + t = m_pulldown(*mp, off, len, &toff); + if (t == NULL) { + *mp = NULL; + return (NULL); + } + return (mtod(t, caddr_t) + toff); +} #endif /* _KERNEL */ #endif /* _NETINET_IP6_H_ */ Index: netinet/tcp_input.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_input.c,v diff -u -p -r1.448 tcp_input.c --- netinet/tcp_input.c 24 May 2025 12:27:23 -0000 1.448 +++ netinet/tcp_input.c 24 May 2025 14:08:47 -0000 @@ -448,8 +448,8 @@ tcp_input_solocked(struct mbuf **mp, int * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ - IP6_EXTHDR_GET(th, struct tcphdr *, mp, iphlen, sizeof(*th)); - if (!th) { + th = ip6_exthdr_get(mp, iphlen, sizeof(*th)); + if (th == NULL) { tcpstat_inc(tcps_rcvshort); return IPPROTO_DONE; } @@ -532,8 +532,8 @@ tcp_input_solocked(struct mbuf **mp, int } tlen -= off; if (off > sizeof(struct tcphdr)) { - IP6_EXTHDR_GET(th, struct tcphdr *, mp, iphlen, off); - if (!th) { + th = ip6_exthdr_get(mp, iphlen, off); + if (th == NULL) { tcpstat_inc(tcps_rcvshort); return IPPROTO_DONE; } Index: netinet/udp_usrreq.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/udp_usrreq.c,v diff -u -p -r1.338 udp_usrreq.c --- netinet/udp_usrreq.c 24 May 2025 12:27:23 -0000 1.338 +++ netinet/udp_usrreq.c 24 May 2025 14:09:18 -0000 @@ -213,8 +213,8 @@ udp_input(struct mbuf **mp, int *offp, i udpstat_inc(udps_ipackets); - IP6_EXTHDR_GET(uh, struct udphdr *, mp, iphlen, sizeof(struct udphdr)); - if (!uh) { + uh = ip6_exthdr_get(mp, iphlen, sizeof(struct udphdr)); + if (uh == NULL) { udpstat_inc(udps_hdrops); return IPPROTO_DONE; } Index: netinet6/dest6.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/dest6.c,v diff -u -p -r1.22 dest6.c --- netinet6/dest6.c 24 May 2025 12:27:23 -0000 1.22 +++ netinet6/dest6.c 24 May 2025 14:10:09 -0000 @@ -57,12 +57,12 @@ dest6_input(struct mbuf **mp, int *offp, u_int8_t *opt; /* validation of the length of the header */ - IP6_EXTHDR_GET(dstopts, struct ip6_dest *, mp, off, sizeof(*dstopts)); + dstopts = ip6_exthdr_get(mp, off, sizeof(*dstopts)); if (dstopts == NULL) return IPPROTO_DONE; dstoptlen = (dstopts->ip6d_len + 1) << 3; - IP6_EXTHDR_GET(dstopts, struct ip6_dest *, mp, off, dstoptlen); + dstopts = ip6_exthdr_get(mp, off, dstoptlen); if (dstopts == NULL) return IPPROTO_DONE; off += dstoptlen; Index: netinet6/frag6.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/frag6.c,v diff -u -p -r1.91 frag6.c --- netinet6/frag6.c 24 May 2025 12:27:23 -0000 1.91 +++ netinet6/frag6.c 24 May 2025 14:15:34 -0000 @@ -125,7 +125,7 @@ frag6_input(struct mbuf **mp, int *offp, u_int8_t ecn, ecn0; ip6 = mtod(*mp, struct ip6_hdr *); - IP6_EXTHDR_GET(ip6f, struct ip6_frag *, mp, offset, sizeof(*ip6f)); + ip6f = ip6_exthdr_get(mp, offset, sizeof(*ip6f)); if (ip6f == NULL) return IPPROTO_DONE; @@ -451,8 +451,7 @@ frag6_input(struct mbuf **mp, int *offp, int prvnxt = ip6_get_prevhdr(*mp, offset); uint8_t *prvnxtp; - IP6_EXTHDR_GET(prvnxtp, uint8_t *, mp, prvnxt, - sizeof(*prvnxtp)); + prvnxtp = ip6_exthdr_get(mp, prvnxt, sizeof(*prvnxtp)); if (prvnxtp == NULL) goto dropfrag; *prvnxtp = nxt; Index: netinet6/icmp6.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/icmp6.c,v diff -u -p -r1.265 icmp6.c --- netinet6/icmp6.c 24 May 2025 12:27:23 -0000 1.265 +++ netinet6/icmp6.c 24 May 2025 14:14:28 -0000 @@ -281,8 +281,7 @@ icmp6_do_error(struct mbuf *m, int type, if (off >= 0 && nxt == IPPROTO_ICMPV6) { struct icmp6_hdr *icp; - IP6_EXTHDR_GET(icp, struct icmp6_hdr *, &m, off, - sizeof(*icp)); + icp = ip6_exthdr_get(&m, off, sizeof(*icp)); if (icp == NULL) { icmp6stat_inc(icp6s_tooshort); return (NULL); @@ -407,7 +406,7 @@ icmp6_input(struct mbuf **mp, int *offp, /* * calculate the checksum */ - IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, mp, off, sizeof(*icmp6)); + icmp6 = ip6_exthdr_get(mp, off, sizeof(*icmp6)); if (icmp6 == NULL) { icmp6stat_inc(icp6s_tooshort); return IPPROTO_DONE; @@ -588,8 +587,7 @@ icmp6_input(struct mbuf **mp, int *offp, n->m_next = n0; } else { deliverecho: - IP6_EXTHDR_GET(nicmp6, struct icmp6_hdr *, &n, off, - sizeof(*nicmp6)); + nicmp6 = ip6_exthdr_get(&n, off, sizeof(*nicmp6)); noff = off; } if (n) { @@ -762,8 +760,8 @@ icmp6_notify_error(struct mbuf *m, int o icmp6stat_inc(icp6s_tooshort); goto freeit; } - IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, &m, off, - sizeof(*icmp6) + sizeof(struct ip6_hdr)); + icmp6 = ip6_exthdr_get(&m, off, + sizeof(*icmp6) + sizeof(struct ip6_hdr)); if (icmp6 == NULL) { icmp6stat_inc(icp6s_tooshort); return (-1); @@ -791,8 +789,7 @@ icmp6_notify_error(struct mbuf *m, int o case IPPROTO_HOPOPTS: case IPPROTO_DSTOPTS: case IPPROTO_AH: - IP6_EXTHDR_GET(eh, struct ip6_ext *, &m, - eoff, sizeof(*eh)); + eh = ip6_exthdr_get(&m, eoff, sizeof(*eh)); if (eh == NULL) { icmp6stat_inc(icp6s_tooshort); return (-1); @@ -813,8 +810,7 @@ icmp6_notify_error(struct mbuf *m, int o * information that depends on the final * destination (e.g. path MTU). */ - IP6_EXTHDR_GET(rth, struct ip6_rthdr *, &m, - eoff, sizeof(*rth)); + rth = ip6_exthdr_get(&m, eoff, sizeof(*rth)); if (rth == NULL) { icmp6stat_inc(icp6s_tooshort); return (-1); @@ -832,24 +828,23 @@ icmp6_notify_error(struct mbuf *m, int o rth->ip6r_type == IPV6_RTHDR_TYPE_0) { int hops; - IP6_EXTHDR_GET(rth0, - struct ip6_rthdr0 *, &m, - eoff, rthlen); + rth0 = ip6_exthdr_get(&m, eoff, rthlen); if (rth0 == NULL) { icmp6stat_inc(icp6s_tooshort); return (-1); } /* just ignore a bogus header */ if ((rth0->ip6r0_len % 2) == 0 && - (hops = rth0->ip6r0_len/2)) - finaldst = (struct in6_addr *)(rth0 + 1) + (hops - 1); + (hops = rth0->ip6r0_len/2)) { + finaldst = (struct in6_addr *) + (rth0 + 1) + (hops - 1); + } } eoff += rthlen; nxt = rth->ip6r_nxt; break; case IPPROTO_FRAGMENT: - IP6_EXTHDR_GET(fh, struct ip6_frag *, &m, - eoff, sizeof(*fh)); + fh = ip6_exthdr_get(&m, eoff, sizeof(*fh)); if (fh == NULL) { icmp6stat_inc(icp6s_tooshort); return (-1); @@ -879,8 +874,8 @@ icmp6_notify_error(struct mbuf *m, int o } } notify: - IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, &m, off, - sizeof(*icmp6) + sizeof(struct ip6_hdr)); + icmp6 = ip6_exthdr_get(&m, off, + sizeof(*icmp6) + sizeof(struct ip6_hdr)); if (icmp6 == NULL) { icmp6stat_inc(icp6s_tooshort); return (-1); @@ -1204,7 +1199,7 @@ icmp6_redirect_input(struct mbuf *m, int if (!(ifp->if_xflags & IFXF_AUTOCONF6)) goto freeit; - IP6_EXTHDR_GET(nd_rd, struct nd_redirect *, &m, off, icmp6len); + nd_rd = ip6_exthdr_get(&m, off, icmp6len); if (nd_rd == NULL) { icmp6stat_inc(icp6s_tooshort); if_put(ifp); Index: netinet6/ip6_input.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/ip6_input.c,v diff -u -p -r1.271 ip6_input.c --- netinet6/ip6_input.c 24 May 2025 12:27:23 -0000 1.271 +++ netinet6/ip6_input.c 24 May 2025 14:19:44 -0000 @@ -685,8 +685,8 @@ ip6_hbhchcheck(struct mbuf **mp, int *of (caddr_t)&ip6->ip6_plen - (caddr_t)ip6); goto bad; } - IP6_EXTHDR_GET(hbh, struct ip6_hbh *, mp, - sizeof(struct ip6_hdr), sizeof(struct ip6_hbh)); + hbh = ip6_exthdr_get(mp, sizeof(struct ip6_hdr), + sizeof(struct ip6_hbh)); if (hbh == NULL) { ip6stat_inc(ip6s_tooshort); goto bad; @@ -814,15 +814,14 @@ ip6_hopopts_input(struct mbuf **mp, int struct ip6_hbh *hbh; /* validation of the length of the header */ - IP6_EXTHDR_GET(hbh, struct ip6_hbh *, mp, - sizeof(struct ip6_hdr), sizeof(struct ip6_hbh)); + hbh = ip6_exthdr_get(mp, sizeof(struct ip6_hdr), + sizeof(struct ip6_hbh)); if (hbh == NULL) { ip6stat_inc(ip6s_tooshort); return -1; } hbhlen = (hbh->ip6h_len + 1) << 3; - IP6_EXTHDR_GET(hbh, struct ip6_hbh *, mp, sizeof(struct ip6_hdr), - hbhlen); + hbh = ip6_exthdr_get(mp, sizeof(struct ip6_hdr), hbhlen); if (hbh == NULL) { ip6stat_inc(ip6s_tooshort); return -1; Index: netinet6/mld6.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/mld6.c,v diff -u -p -r1.66 mld6.c --- netinet6/mld6.c 24 May 2025 12:27:23 -0000 1.66 +++ netinet6/mld6.c 24 May 2025 14:15:51 -0000 @@ -179,7 +179,7 @@ mld6_input(struct mbuf *m, int off) /* XXX: These are necessary for KAME's link-local hack */ struct in6_addr all_nodes = IN6ADDR_LINKLOCAL_ALLNODES_INIT; - IP6_EXTHDR_GET(mldh, struct mld_hdr *, &m, off, sizeof(*mldh)); + mldh = ip6_exthdr_get(&m, off, sizeof(*mldh)); if (mldh == NULL) { icmp6stat_inc(icp6s_tooshort); return; Index: netinet6/nd6_nbr.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/nd6_nbr.c,v diff -u -p -r1.159 nd6_nbr.c --- netinet6/nd6_nbr.c 24 May 2025 12:27:23 -0000 1.159 +++ netinet6/nd6_nbr.c 24 May 2025 14:16:32 -0000 @@ -117,7 +117,7 @@ nd6_ns_input(struct mbuf *m, int off, in if (ifp == NULL) goto freeit; - IP6_EXTHDR_GET(nd_ns, struct nd_neighbor_solicit *, &m, off, icmp6len); + nd_ns = ip6_exthdr_get(&m, off, icmp6len); if (nd_ns == NULL) { icmp6stat_inc(icp6s_tooshort); if_put(ifp); @@ -540,7 +540,7 @@ nd6_na_input(struct mbuf *m, int off, in if (ip6->ip6_hlim != 255) goto bad; - IP6_EXTHDR_GET(nd_na, struct nd_neighbor_advert *, &m, off, icmp6len); + nd_na = ip6_exthdr_get(&m, off, icmp6len); if (nd_na == NULL) { icmp6stat_inc(icp6s_tooshort); if_put(ifp); Index: netinet6/nd6_rtr.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/nd6_rtr.c,v diff -u -p -r1.174 nd6_rtr.c --- netinet6/nd6_rtr.c 24 May 2025 12:27:24 -0000 1.174 +++ netinet6/nd6_rtr.c 24 May 2025 14:17:58 -0000 @@ -92,8 +92,7 @@ nd6_rtr_cache(struct mbuf *m, int off, i if (IN6_IS_ADDR_UNSPECIFIED(&saddr6)) goto freeit; - IP6_EXTHDR_GET(nd_rs, struct nd_router_solicit *, &m, off, - icmp6len); + nd_rs = ip6_exthdr_get(&m, off, icmp6len); if (nd_rs == NULL) { icmp6stat_inc(icp6s_tooshort); return; @@ -109,8 +108,7 @@ nd6_rtr_cache(struct mbuf *m, int off, i if (!IN6_IS_ADDR_LINKLOCAL(&saddr6)) goto bad; - IP6_EXTHDR_GET(nd_ra, struct nd_router_advert *, &m, off, - icmp6len); + nd_ra = ip6_exthdr_get(&m, off, icmp6len); if (nd_ra == NULL) { icmp6stat_inc(icp6s_tooshort); return; Index: netinet6/raw_ip6.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/raw_ip6.c,v diff -u -p -r1.191 raw_ip6.c --- netinet6/raw_ip6.c 24 May 2025 12:27:24 -0000 1.191 +++ netinet6/raw_ip6.c 24 May 2025 14:20:04 -0000 @@ -147,8 +147,7 @@ rip6_input(struct mbuf **mp, int *offp, if (proto == IPPROTO_ICMPV6) { struct icmp6_hdr *icmp6; - IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, mp, *offp, - sizeof(*icmp6)); + icmp6 = ip6_exthdr_get(mp, *offp, sizeof(*icmp6)); if (icmp6 == NULL) return IPPROTO_DONE; type = icmp6->icmp6_type; Index: netinet6/route6.c =================================================================== RCS file: /data/mirror/openbsd/cvs/src/sys/netinet6/route6.c,v diff -u -p -r1.24 route6.c --- netinet6/route6.c 24 May 2025 12:27:24 -0000 1.24 +++ netinet6/route6.c 24 May 2025 14:20:27 -0000 @@ -59,7 +59,7 @@ route6_input(struct mbuf **mp, int *offp int off = *offp, rhlen; ip6 = mtod(*mp, struct ip6_hdr *); - IP6_EXTHDR_GET(rh, struct ip6_rthdr *, mp, off, sizeof(*rh)); + rh = ip6_exthdr_get(mp, off, sizeof(*rh)); if (rh == NULL) { ip6stat_inc(ip6s_tooshort); return IPPROTO_DONE;