Function esp_output

freebsd/netipsec/xform_esp.c:672–961

* ESP output routine, called by ipsec[46]_perform_request(). */

 * ESP output routine, called by ipsec[46]_perform_request().
 */
static int
esp_output(struct mbuf *m, struct secpolicy *sp, struct secasvar *sav,
    u_int idx, int skip, int protoff)
{
	IPSEC_DEBUG_DECLARE(char buf[IPSEC_ADDRSTRLEN]);
	struct cryptop *crp;
	const struct auth_hash *esph;
	const struct enc_xform *espx;
	struct mbuf *mo = NULL;
	struct xform_data *xd;
	struct secasindex *saidx;
	unsigned char *pad;
	uint8_t *ivp;
	uint64_t cntr;
	crypto_session_t cryptoid;
	int hlen, rlen, padding, blks, alen, i, roff;
	int error, maxpacketsize;
	uint8_t prot;
	uint32_t seqh;
	const struct crypto_session_params *csp;

	IPSEC_ASSERT(sav != NULL, ("null SA"));
	esph = sav->tdb_authalgxform;
	espx = sav->tdb_encalgxform;
	IPSEC_ASSERT(espx != NULL, ("null encoding xform"));

	if (sav->flags & SADB_X_EXT_OLD)
		hlen = sizeof (struct esp) + sav->ivlen;
	else
		hlen = sizeof (struct newesp) + sav->ivlen;

	rlen = m->m_pkthdr.len - skip;	/* Raw payload length. */
	/*
	 * RFC4303 2.4 Requires 4 byte alignment.
	 * Old versions of FreeBSD can't decrypt partial blocks encrypted
	 * with AES-CTR. Align payload to native_blocksize (16 bytes)
	 * in order to preserve compatibility.
	 */
	if (SAV_ISCTR(sav) && V_esp_ctr_compatibility)
		blks = MAX(4, espx->native_blocksize);	/* Cipher blocksize */
	else
		blks = MAX(4, espx->blocksize);

	/* XXX clamp padding length a la KAME??? */
	padding = ((blks - ((rlen + 2) % blks)) % blks) + 2;

	alen = xform_ah_authsize(esph);

	ESPSTAT_INC(esps_output);

	saidx = &sav->sah->saidx;
	/* Check for maximum packet size violations. */
	switch (saidx->dst.sa.sa_family) {
#ifdef INET
	case AF_INET:
		maxpacketsize = IP_MAXPACKET;
		break;
#endif /* INET */