Correctly handle the padding for IPv6-AH, as specified by RFC4302. Seen in
a FreeBSD bug report, by Jason Mader. The RFC specifies that under IPv6 the complete AH header must be 64bit- aligned, and under IPv4 32bit-aligned. That's a rule we've never respected. The other BSDs and MacOS never have either. So respect it now. This makes it possible to set up IPv6-AH between Linux and NetBSD, and also probably between Windows and NetBSD. Until now all the tests I made were between two *BSD hosts, and everything worked "correctly" since both hosts were speaking the same non-standard AHv6, so they could understand each other. Tested with Fedora<->NetBSD, hmac-sha2-384.
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maxv
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6abbe0506f
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@ -1,4 +1,4 @@
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/* $NetBSD: xform_ah.c,v 1.104 2018/05/30 17:17:11 maxv Exp $ */
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/* $NetBSD: xform_ah.c,v 1.105 2018/05/30 18:02:40 maxv Exp $ */
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/* $FreeBSD: xform_ah.c,v 1.1.4.1 2003/01/24 05:11:36 sam Exp $ */
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/* $OpenBSD: ip_ah.c,v 1.63 2001/06/26 06:18:58 angelos Exp $ */
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/*
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@ -39,7 +39,7 @@
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: xform_ah.c,v 1.104 2018/05/30 17:17:11 maxv Exp $");
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__KERNEL_RCSID(0, "$NetBSD: xform_ah.c,v 1.105 2018/05/30 18:02:40 maxv Exp $");
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#if defined(_KERNEL_OPT)
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#include "opt_inet.h"
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@ -167,11 +167,21 @@ ah_hdrsiz(const struct secasvar *sav)
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size_t size;
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if (sav != NULL) {
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int authsize;
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int authsize, rplen, align;
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KASSERT(sav->tdb_authalgxform != NULL);
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/*XXX not right for null algorithm--does it matter??*/
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/* RFC4302: use the correct alignment. */
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align = sizeof(uint32_t);
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#ifdef INET6
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if (sav->sah->saidx.dst.sa.sa_family == AF_INET6) {
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align = sizeof(uint64_t);
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}
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#endif
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rplen = HDRSIZE(sav);
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authsize = AUTHSIZE(sav);
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size = roundup(authsize, sizeof(uint32_t)) + HDRSIZE(sav);
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size = roundup(rplen + authsize, align);
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} else {
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/* default guess */
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size = sizeof(struct ah) + sizeof(uint32_t) + ah_max_authsize;
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@ -520,7 +530,7 @@ ah_input(struct mbuf *m, struct secasvar *sav, int skip, int protoff)
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const struct auth_hash *ahx;
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struct tdb_crypto *tc = NULL;
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struct newah *ah;
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int hl, rplen, authsize, error, stat = AH_STAT_HDROPS;
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int hl, rplen, authsize, ahsize, error, stat = AH_STAT_HDROPS;
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struct cryptodesc *crda;
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struct cryptop *crp = NULL;
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bool pool_used;
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@ -553,25 +563,26 @@ ah_input(struct mbuf *m, struct secasvar *sav, int skip, int protoff)
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}
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/* Verify AH header length. */
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hl = ah->ah_len * sizeof(uint32_t);
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hl = sizeof(struct ah) + (ah->ah_len * sizeof(uint32_t));
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ahx = sav->tdb_authalgxform;
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authsize = AUTHSIZE(sav);
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if (hl != authsize + rplen - sizeof(struct ah)) {
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ahsize = ah_hdrsiz(sav);
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if (hl != ahsize) {
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char buf[IPSEC_ADDRSTRLEN];
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DPRINTF(("%s: bad authenticator length %u (expecting %lu)"
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" for packet in SA %s/%08lx\n", __func__,
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hl, (u_long) (authsize + rplen - sizeof(struct ah)),
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hl, (u_long)ahsize,
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ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
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(u_long) ntohl(sav->spi)));
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stat = AH_STAT_BADAUTHL;
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error = EACCES;
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goto bad;
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}
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if (skip + authsize + rplen > m->m_pkthdr.len) {
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if (skip + ahsize > m->m_pkthdr.len) {
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char buf[IPSEC_ADDRSTRLEN];
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DPRINTF(("%s: bad mbuf length %u (expecting >= %lu)"
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" for packet in SA %s/%08lx\n", __func__,
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m->m_pkthdr.len, (u_long)(skip + authsize + rplen),
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m->m_pkthdr.len, (u_long)(skip + ahsize),
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ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
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(u_long) ntohl(sav->spi)));
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stat = AH_STAT_BADAUTHL;
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@ -720,7 +731,7 @@ static int
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ah_input_cb(struct cryptop *crp)
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{
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char buf[IPSEC_ADDRSTRLEN];
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int rplen, error, skip, protoff;
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int rplen, ahsize, error, skip, protoff;
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unsigned char calc[AH_ALEN_MAX];
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struct mbuf *m;
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struct tdb_crypto *tc;
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@ -751,6 +762,7 @@ ah_input_cb(struct cryptop *crp)
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/* Figure out header size. */
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rplen = HDRSIZE(sav);
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authsize = AUTHSIZE(sav);
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ahsize = ah_hdrsiz(sav);
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size = sizeof(*tc) + skip + rplen + authsize;
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if (__predict_true(size <= ah_pool_item_size))
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@ -844,7 +856,7 @@ ah_input_cb(struct cryptop *crp)
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/*
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* Remove the AH header and authenticator from the mbuf.
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*/
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error = m_striphdr(m, skip, rplen + authsize);
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error = m_striphdr(m, skip, ahsize);
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if (error) {
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DPRINTF(("%s: mangled mbuf chain for SA %s/%08lx\n", __func__,
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ipsec_address(&saidx->dst, buf, sizeof(buf)),
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@ -891,7 +903,7 @@ ah_output(struct mbuf *m, const struct ipsecrequest *isr, struct secasvar *sav,
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struct mbuf *mi;
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struct cryptop *crp;
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uint16_t iplen;
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int error, rplen, authsize, maxpacketsize, roff;
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int error, rplen, authsize, ahsize, maxpacketsize, roff;
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uint8_t prot;
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struct newah *ah;
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size_t ipoffs;
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@ -905,6 +917,8 @@ ah_output(struct mbuf *m, const struct ipsecrequest *isr, struct secasvar *sav,
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/* Figure out header size. */
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rplen = HDRSIZE(sav);
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authsize = AUTHSIZE(sav);
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ahsize = ah_hdrsiz(sav);
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/* Check for maximum packet size violations. */
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switch (sav->sah->saidx.dst.sa.sa_family) {
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@ -930,13 +944,12 @@ ah_output(struct mbuf *m, const struct ipsecrequest *isr, struct secasvar *sav,
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error = EPFNOSUPPORT;
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goto bad;
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}
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authsize = AUTHSIZE(sav);
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if (rplen + authsize + m->m_pkthdr.len > maxpacketsize) {
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if (ahsize + m->m_pkthdr.len > maxpacketsize) {
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DPRINTF(("%s: packet in SA %s/%08lx got too big "
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"(len %u, max len %u)\n", __func__,
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ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
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(u_long) ntohl(sav->spi),
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rplen + authsize + m->m_pkthdr.len, maxpacketsize));
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ahsize + m->m_pkthdr.len, maxpacketsize));
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AH_STATINC(AH_STAT_TOOBIG);
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error = EMSGSIZE;
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goto bad;
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@ -956,11 +969,10 @@ ah_output(struct mbuf *m, const struct ipsecrequest *isr, struct secasvar *sav,
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}
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/* Inject AH header. */
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mi = m_makespace(m, skip, rplen + authsize, &roff);
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mi = m_makespace(m, skip, ahsize, &roff);
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if (mi == NULL) {
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DPRINTF(("%s: failed to inject %u byte AH header for SA "
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"%s/%08lx\n", __func__,
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rplen + authsize,
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"%s/%08lx\n", __func__, ahsize,
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ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
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(u_long) ntohl(sav->spi)));
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AH_STATINC(AH_STAT_HDROPS);
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@ -976,13 +988,17 @@ ah_output(struct mbuf *m, const struct ipsecrequest *isr, struct secasvar *sav,
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/* Initialize the AH header. */
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m_copydata(m, protoff, sizeof(uint8_t), &ah->ah_nxt);
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ah->ah_len = (rplen + authsize - sizeof(struct ah)) / sizeof(uint32_t);
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ah->ah_len = (ahsize - sizeof(struct ah)) / sizeof(uint32_t);
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ah->ah_reserve = 0;
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ah->ah_spi = sav->spi;
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/* Zeroize authenticator. */
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m_copyback(m, skip + rplen, authsize, ipseczeroes);
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/* Zeroize padding. */
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m_copyback(m, skip + rplen + authsize, ahsize - (rplen + authsize),
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ipseczeroes);
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/* Insert packet replay counter, as requested. */
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if (sav->replay) {
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if (sav->replay->count == ~0 &&
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@ -1051,7 +1067,7 @@ ah_output(struct mbuf *m, const struct ipsecrequest *isr, struct secasvar *sav,
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* header length as it will be fixed by our caller.
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*/
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memcpy(&iplen, pext + ipoffs, sizeof(iplen));
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iplen = htons(ntohs(iplen) + rplen + authsize);
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iplen = htons(ntohs(iplen) + ahsize);
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m_copyback(m, ipoffs, sizeof(iplen), &iplen);
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/* Fix the Next Header field in saved header. */
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