/*      $NetBSD: ether_sw_offload.c,v 1.9 2024/09/15 08:33:13 andvar Exp $      */

/*
* Copyright (c) 2018 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Rin Okuyama.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#endif

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ether_sw_offload.c,v 1.9 2024/09/15 08:33:13 andvar Exp $");

#include <sys/param.h>
#include <sys/types.h>
#include <sys/mbuf.h>
#include <sys/syslog.h>
#include <sys/time.h>

#include <net/if.h>
#include <net/if_ether.h>
#include <net/ether_sw_offload.h>

#include <netinet/in.h>
#include <netinet/in_offload.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>

#ifdef INET6
#include <netinet/ip6.h>
#include <netinet6/in6.h>
#include <netinet6/in6_offload.h>
#endif

/*
* Limit error messages at most once per 10 seconds.
*/
static const struct timeval eso_err_interval = {
       .tv_sec = 10,
       .tv_usec = 0,
};
static struct timeval eso_err_lasttime;

/*
* Handle TX offload in software. For TSO, split the packet into
* chunks with payloads of size MSS. For checksum offload, update
* required checksum fields. The results are more than one packet
* in general. Return a mbuf queue consists of them.
*/

struct mbuf *
ether_sw_offload_tx(struct ifnet *ifp, struct mbuf *m)
{
       struct ether_header *ep;
       int flags, ehlen;
       uint16_t type;
#ifdef INET6
       bool v6;
#else
       bool v6 __diagused;
#endif

       KASSERT(m->m_flags & M_PKTHDR);
       flags = m->m_pkthdr.csum_flags;
       if (flags == 0)
               goto done;

       /* Sanity check */
       if (!TX_OFFLOAD_SUPPORTED(ifp->if_csum_flags_tx, flags))
               goto quit;

       KASSERT(m->m_pkthdr.len >= sizeof(*ep));
       KASSERT(m->m_len >= sizeof(*ep));
       ep = mtod(m, struct ether_header *);
       switch (type = ntohs(ep->ether_type)) {
       case ETHERTYPE_IP:
       case ETHERTYPE_IPV6:
               ehlen = ETHER_HDR_LEN;
               break;
       case ETHERTYPE_VLAN:
               ehlen = ETHER_HDR_LEN + ETHER_VLAN_ENCAP_LEN;
               break;
       default:
               if (ratecheck(&eso_err_lasttime, &eso_err_interval))
                       log(LOG_ERR, "%s: %s: dropping invalid frame "
                           "type 0x%04hx csum_flags 0x%08x\n",
                           __func__, ifp->if_xname, type, flags);
               goto quit;
       }
       KASSERT(m->m_pkthdr.len >= ehlen);

       v6 = flags & (M_CSUM_TSOv6 | M_CSUM_TCPv6 | M_CSUM_UDPv6);
#ifndef INET6
       KASSERT(!v6);
#endif

       if (flags & (M_CSUM_TSOv4 | M_CSUM_TSOv6)) {
               /*
                * tcp[46]_segment() assume that size of payloads is
                * a multiple of MSS. Further, tcp6_segment() assumes
                * no extension headers.
                *
                * XXX Do we need some KASSERT's?
                */
#ifdef INET6
               if (v6)
                       return tcp6_segment(m, ehlen);
               else
#endif
                       return tcp4_segment(m, ehlen);
       }

#ifdef INET6
       if (v6)
               in6_undefer_cksum(m, ehlen, flags);
       else
#endif
               in_undefer_cksum(m, ehlen, flags);
done:
       m->m_pkthdr.csum_flags = 0;
       m->m_nextpkt = NULL;
       return m;
quit:
       m_freem(m);
       return NULL;
}

/*
* Handle RX offload in software.
*
* XXX Fragmented packets or packets with IPv6 extension headers
* are not currently supported.
*/

struct mbuf *
ether_sw_offload_rx(struct ifnet *ifp, struct mbuf *m)
{
       struct ether_header *eh;
       struct ip *ip;
       struct tcphdr *th;
       struct udphdr *uh;
       uint16_t sum, osum;
       uint8_t proto;
       int flags, enabled, len, ehlen, iphlen, l4offset;
       bool v6;

       flags = 0;

       enabled = ifp->if_csum_flags_rx;
       if (!(enabled & (M_CSUM_IPv4 | M_CSUM_TCPv4 | M_CSUM_UDPv4 |
           M_CSUM_TCPv6 | M_CSUM_UDPv6)))
               goto done;

       KASSERT(m->m_flags & M_PKTHDR);
       len = m->m_pkthdr.len;

       KASSERT(len >= sizeof(*eh));
       if (m->m_len < sizeof(*eh)) {
               m = m_pullup(m, sizeof(*eh));
               if (m == NULL)
                       return NULL;
       }
       eh = mtod(m, struct ether_header *);
       switch (htons(eh->ether_type)) {
       case ETHERTYPE_IP:
       case ETHERTYPE_IPV6:
               ehlen = ETHER_HDR_LEN;
               break;
       case ETHERTYPE_VLAN:
               ehlen = ETHER_HDR_LEN + ETHER_VLAN_ENCAP_LEN;
               break;
       default:
               goto done;
       }

       KASSERT(len >= ehlen);
       len = m->m_pkthdr.len - ehlen;

       KASSERT(len >= sizeof(*ip));
       if (m->m_len < ehlen + sizeof(*ip)) {
               m = m_pullup(m, ehlen + sizeof(*ip));
               if (m == NULL)
                       return NULL;
       }
       ip = (void *)(mtod(m, char *) + ehlen);
       v6 = (ip->ip_v != IPVERSION);

       if (v6) {
#ifdef INET6
               struct ip6_hdr *ip6;

               KASSERT(len >= sizeof(*ip6));
               if (m->m_len < ehlen + sizeof(*ip6)) {
                       m = m_pullup(m, ehlen + sizeof(*ip6));
                       if (m == NULL)
                               return NULL;
               }
               ip6 = (void *)(mtod(m, char *) + ehlen);
               KASSERT((ip6->ip6_vfc & IPV6_VERSION_MASK) == IPV6_VERSION);

               iphlen = sizeof(*ip6);

               len -= iphlen;

               proto = ip6->ip6_nxt;
               switch (proto) {
               case IPPROTO_TCP:
                       if (!(enabled & M_CSUM_TCPv6))
                               goto done;
                       break;
               case IPPROTO_UDP:
                       if (!(enabled & M_CSUM_UDPv6))
                               goto done;
                       break;
               default:
                       /* XXX Extension headers are not supported. */
                       goto done;
               }

               sum = in6_cksum_phdr(&ip6->ip6_src, &ip6->ip6_dst, htonl(len),
                   htonl(proto));
#else
               goto done;
#endif
       } else {
               if (enabled & M_CSUM_IPv4)
                       flags |= M_CSUM_IPv4;

               iphlen = ip->ip_hl << 2;
               KASSERT(iphlen >= sizeof(*ip));

               len -= iphlen;
               KASSERT(len >= 0);

               if (in4_cksum(m, 0, ehlen, iphlen) != 0) {
                       if (enabled & M_CSUM_IPv4)
                               flags |= M_CSUM_IPv4_BAD;
                       /* Broken. Do not check further. */
                       goto done;
               }

               /* Check if fragmented. */
               if (ntohs(ip->ip_off) & ~(IP_DF | IP_RF))
                       goto done;

               proto = ip->ip_p;
               switch (proto) {
               case IPPROTO_TCP:
                       if (!(enabled & M_CSUM_TCPv4))
                               goto done;
                       break;
               case IPPROTO_UDP:
                       if (!(enabled & M_CSUM_UDPv4))
                               goto done;
                       break;
               default:
                       goto done;
               }

               sum = in_cksum_phdr(ip->ip_src.s_addr, ip->ip_dst.s_addr,
                   htons((uint16_t)len + proto));
       }

       l4offset = ehlen + iphlen;
       switch (proto) {
       case IPPROTO_TCP:
               KASSERT(len >= sizeof(*th));
               if (m->m_len < l4offset + sizeof(*th)) {
                       m = m_pullup(m, l4offset + sizeof(*th));
                       if (m == NULL)
                               return NULL;
               }
               th = (void *)(mtod(m, char *) + l4offset);
               osum = th->th_sum;
               th->th_sum = sum;
#ifdef INET6
               if (v6) {
                       flags |= M_CSUM_TCPv6;
                       sum = in6_cksum(m, 0, l4offset, len);
               } else
#endif
               {
                       flags |= M_CSUM_TCPv4;
                       sum = in4_cksum(m, 0, l4offset, len);
               }
               if (sum != osum)
                       flags |= M_CSUM_TCP_UDP_BAD;
               th->th_sum = osum;
               break;
       case IPPROTO_UDP:
               KASSERT(len >= sizeof(*uh));
               if (m->m_len < l4offset + sizeof(*uh)) {
                       m = m_pullup(m, l4offset + sizeof(*uh));
                       if (m == NULL)
                               return NULL;
               }
               uh = (void *)(mtod(m, char *) + l4offset);
               osum = uh->uh_sum;
               if (osum == 0)
                       break;
               uh->uh_sum = sum;
#ifdef INET6
               if (v6) {
                       flags |= M_CSUM_UDPv6;
                       sum = in6_cksum(m, 0, l4offset, len);
               } else
#endif
               {
                       flags |= M_CSUM_UDPv4;
                       sum = in4_cksum(m, 0, l4offset, len);
               }
               if (sum == 0)
                       sum = 0xffff;
               if (sum != osum)
                       flags |= M_CSUM_TCP_UDP_BAD;
               uh->uh_sum = osum;
               break;
       default:
               panic("%s: impossible", __func__);
       }

done:
       m->m_pkthdr.csum_flags = flags;
       return m;
}

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