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[minix3.git] / minix / net / lwip / pktsock.c

/* LWIP service - pktsock.c - packet code shared between UDP and RAW */

#include "lwip.h"
#include "pktsock.h"
#include "ifaddr.h"

/*
 * This buffer should be much bigger (at least 10KB, according to RFC 3542),
 * but we do not support the ancillary options that take so much space anyway.
 */
#define PKTSOCK_CTLBUF_SIZE             256

static char pktsock_ctlbuf[PKTSOCK_CTLBUF_SIZE];

/*
 * Header structures with ancillary data for received packets.  The reason that
 * we do not simply use a generic pkthdr structure with ip_addr_t source and
 * destination addresses, is that for UDP packets, we put this structure in
 * place of the received (ethernet and IP headers), and such a full structure
 * (including IPv6-size addresses) would not fit in the header space for IPv4
 * packets.  So instead we use two address structures, one for IPv4 and one for
 * IPv6, and a generic header structure on top of it, which also identifies
 * which address structure is underneath.  The combination of the address
 * structure and the header structure must fit in the IP header.  The IPv6
 * packet header is already so close to the limit here that we have to use
 * packed addresses.  For IPv4 we use the regular addresses for simplicity.
 */
struct pkthdr {
        uint16_t port;                  /* source port number (UDP only) */
        uint8_t dstif;                  /* interface that received the pkt */
        uint8_t addrif;                 /* interface that accepted the pkt */
        uint8_t tos;                    /* TOS/TC value from the IP header */
        uint8_t ttl;                    /* TTL/HL value from the IP header */
        uint8_t flags;                  /* packet flags (PKTHF_) */
        uint8_t _unused;                /* all that is still available.. */
};

#define PKTHF_IPV6              0x01    /* packet has IPv6 header */
#define PKTHF_MCAST             0x02    /* packet has multicast destination */
#define PKTHF_BCAST             0x04    /* packet has broadcast destination */

struct pktaddr4 {
        ip4_addr_t srcaddr;
        ip4_addr_t dstaddr;
};

struct pktaddr6 {
        ip6_addr_p_t srcaddr;
        ip6_addr_p_t dstaddr;
};

/*
 * Create a packet socket.  Relay parameters and return values to and from the
 * IP module's socket creation function.  This function must not allocate any
 * resources in any form, as socket creation may still fail later, in which
 * case no destruction function is called.
 */
int
pktsock_socket(struct pktsock * pkt, int domain, size_t sndbuf, size_t rcvbuf,
        struct sock ** sockp)
{

        pkt->pkt_rcvhead = NULL;
        pkt->pkt_rcvtailp = &pkt->pkt_rcvhead;
        pkt->pkt_rcvlen = 0;

        mcast_reset(&pkt->pkt_mcast);

        memset(&pkt->pkt_srcaddr, 0, sizeof(pkt->pkt_srcaddr));
        pkt->pkt_ifindex = 0;

        /*
         * Any PKTF_ type flags should be initialized on the socket only after
         * the following call, as this call will clear the flags field.  For
         * now, no PKTF_ flags need to be set by default, though.
         */
        return ipsock_socket(&pkt->pkt_ipsock, domain, sndbuf, rcvbuf, sockp);
}

/*
 * Return TRUE if the given packet can and should be received on the given
 * socket, or FALSE if there is a reason not to receive the packet.
 */
static int
pktsock_may_recv(struct pktsock * pkt, struct pbuf * pbuf)
{

        /*
         * By policy, multicast packets should not be received on sockets of
         * which the owning application is not multicast aware.
         */
        if (ip_addr_ismulticast(ip_current_dest_addr()) &&
            !(ipsock_get_flag(&pkt->pkt_ipsock, PKTF_MCAWARE)))
                return FALSE;

        /*
         * Due to fragment reassembly, we might end up with packets that take
         * up more buffer space than their byte size, even after rounding up
         * the latter.  The user probably does not want packets to get dropped
         * for that reason, e.g. when they set a 64K limit and the packet ends
         * up being estimated as 65K and dropped.  So, we test against
         * 'pbuf->tot_len' rather than the rounded-up packet size.  However,
         * 'pkt->pkt_rcvlen' itself is increased by the rounded-up packet size
         * when enqueuing the packet, so that we still count the memory
         * consumption (generally) conservatively, which is what we want.
         */
        return (pkt->pkt_rcvlen + pbuf->tot_len <=
            ipsock_get_rcvbuf(&pkt->pkt_ipsock));
}

/*
 * Check whether the given packet can and should be received on the given
 * socket.  If so, return the amount of space for ancillary information that
 * will be necessary for the packet.  If not, return a negative value.
 */
int
pktsock_test_input(struct pktsock * pkt, struct pbuf * pbuf)
{

        /*
         * This check will be done again in pktsock_input(), but this function
         * is called for raw packets only (not for UDP packets) and, if this
         * (cheap) check fails, we can avoid a (rather expensive) packet copy.
         */
        if (!pktsock_may_recv(pkt, pbuf))
                return -1;

        if (ip_current_is_v6())
                return (int)(sizeof(struct pktaddr6) + sizeof(struct pkthdr));
        else
                return (int)(sizeof(struct pktaddr4) + sizeof(struct pkthdr));
}

/*
 * A packet has arrived on a packet socket.  We own the given packet buffer,
 * and so we must free it if we do not want to keep it.
 */
void
pktsock_input(struct pktsock * pkt, struct pbuf * pbuf,
        const ip_addr_t * srcaddr, uint16_t port)
{
        struct pktaddr4 pktaddr4;
        struct pktaddr6 pktaddr6;
        struct pkthdr pkthdr;
        void *pktaddr;
        struct ifdev *ifdev;
        size_t pktaddrlen;

        /*
         * We are going to mess with the packet's header and contents, so we
         * must be the exclusive owner of the packet.  For UDP packets, lwIP
         * must have made a copy for us in case of non-exclusive delivery
         * (e.g., multicast packets).  For raw packets, we have made a copy of
         * the packet ourselves just before the call to this function.
         */
        if (pbuf->ref != 1)
                panic("input packet has multiple references!");

        /* If the packet should not be received on this socket, drop it. */
        if (!pktsock_may_recv(pkt, pbuf)) {
                pbuf_free(pbuf);

                return;
        }

        /*
         * Enqueue the packet.  Overwrite the leading IP header with packet
         * information that is used at the time of receipt by userland.  The
         * data structures are such that the information always fits in what
         * was the IP header.  The reference count check earlier ensures that
         * we never overwrite part of a packet that is still in use elsewhere.
         */
        if (ip_current_is_v6()) {
                assert(IP_IS_V6(srcaddr));
                assert(ip6_current_dest_addr() != NULL);

                ip6_addr_copy_to_packed(pktaddr6.srcaddr, *ip_2_ip6(srcaddr));
                ip6_addr_copy_to_packed(pktaddr6.dstaddr,
                    *ip6_current_dest_addr());
                pktaddr = &pktaddr6;
                pktaddrlen = sizeof(pktaddr6);

                assert(pktaddrlen + sizeof(pkthdr) <= IP6_HLEN);

                pkthdr.tos = IP6H_TC(ip6_current_header());
                pkthdr.ttl = IP6H_HOPLIM(ip6_current_header());
                pkthdr.flags = PKTHF_IPV6;
        } else {
                assert(IP_IS_V4(srcaddr));
                assert(ip4_current_dest_addr() != NULL);

                memcpy(&pktaddr4.srcaddr, ip_2_ip4(srcaddr),
                    sizeof(pktaddr4.srcaddr));
                memcpy(&pktaddr4.dstaddr, ip4_current_dest_addr(),
                    sizeof(pktaddr4.srcaddr));
                pktaddr = &pktaddr4;
                pktaddrlen = sizeof(pktaddr4);

                assert(pktaddrlen + sizeof(pkthdr) <= IP_HLEN);

                pkthdr.tos = IPH_TOS(ip4_current_header());
                pkthdr.ttl = IPH_TTL(ip4_current_header());
                pkthdr.flags = 0;
        }

        /*
         * Save both the interface on which the packet was received (for
         * PKTINFO) and the interface that owns the destination address of the
         * packet (for the source address's zone ID).
         */
        assert(ip_current_input_netif() != NULL);
        ifdev = netif_get_ifdev(ip_current_input_netif());
        pkthdr.dstif = (uint16_t)ifdev_get_index(ifdev);

        assert(ip_current_netif() != NULL);
        ifdev = netif_get_ifdev(ip_current_netif());
        pkthdr.addrif = (uint16_t)ifdev_get_index(ifdev);

        if ((pbuf->flags & PBUF_FLAG_LLMCAST) ||
            ip_addr_ismulticast(ip_current_dest_addr()))
                pkthdr.flags |= PKTHF_MCAST;
        else if ((pbuf->flags & PBUF_FLAG_LLBCAST) ||
            ip_addr_isbroadcast(ip_current_dest_addr(), ip_current_netif()))
                pkthdr.flags |= PKTHF_BCAST;

        pkthdr.port = port;

        util_pbuf_header(pbuf, sizeof(pkthdr));

        memcpy(pbuf->payload, &pkthdr, sizeof(pkthdr));

        util_pbuf_header(pbuf, pktaddrlen);

        memcpy(pbuf->payload, pktaddr, pktaddrlen);

        util_pbuf_header(pbuf, -(int)(sizeof(pkthdr) + pktaddrlen));

        *pkt->pkt_rcvtailp = pbuf;
        pkt->pkt_rcvtailp = pchain_end(pbuf);
        pkt->pkt_rcvlen += pchain_size(pbuf);

        sockevent_raise(ipsock_get_sock(&pkt->pkt_ipsock), SEV_RECV);
}

/*
 * Obtain interface and source address information for an outgoing packet.  In
 * particular, parse any IPV6_PKTINFO options provided as either sticky options
 * on the socket 'pkt' or as ancillary options in the packet options 'pkto'.
 * On success, return OK, with 'ifdevp' set to either the outgoing interface to
 * use for the packet, or NULL if no outgoing interface was specified using
 * either of the aforementioned options.  If, and only if, 'ifdevp' is set to
 * an actual interface (i.e., not NULL), then 'src_addrp' is filled with either
 * a locally owned, validated, unicast address to use as source of the packet,
 * or the unspecified ('any') address if no source address was specified using
 * the options.  On failure, return a negative error code.
 */
int
pktsock_get_pktinfo(struct pktsock * pkt, struct pktopt * pkto,
        struct ifdev ** ifdevp, ip_addr_t * src_addrp)
{
        struct ifdev *ifdev, *ifdev2;
        ip_addr_t ipaddr;
        uint32_t ifindex;
        int r;

        /* We support only IPV6_PKTINFO.  IP_PKTINFO is not supported. */
        if (!ipsock_is_ipv6(&pkt->pkt_ipsock)) {
                *ifdevp = NULL;
                return OK;
        }

        /*
         * TODO: we are spending a lot of effort on initializing and copying
         * stuff around, even just to find out whether there is anything to do
         * at all here.  See if this can be optimized.
         */
        ip_addr_set_zero_ip6(&ipaddr);

        /*
         * Ancillary data takes precedence over sticky options.  We treat the
         * source address and interface index fields as separate, overriding
         * each earlier value only if non-zero.  TODO: is that correct?
         */
        if (pkto->pkto_flags & PKTOF_PKTINFO) {
                memcpy(ip_2_ip6(&ipaddr)->addr, &pkto->pkto_srcaddr.addr,
                    sizeof(ip_2_ip6(&ipaddr)->addr));
                ifindex = pkto->pkto_ifindex;
        } else
                ifindex = 0;

        if (ip6_addr_isany(ip_2_ip6(&ipaddr)))
                memcpy(ip_2_ip6(&ipaddr)->addr, &pkt->pkt_srcaddr.addr,
                    sizeof(ip_2_ip6(&ipaddr)->addr));
        if (ifindex == 0)
                ifindex = pkt->pkt_ifindex;

        /* If both fields are blank, there is nothing more to do. */
        if (ip6_addr_isany(ip_2_ip6(&ipaddr)) && ifindex == 0) {
                *ifdevp = NULL;
                return OK;
        }

        /* If an interface index is specified, it must be valid. */
        ifdev = NULL;

        if (ifindex != 0 && (ifdev = ifdev_get_by_index(ifindex)) == NULL)
                return ENXIO;

        /*
         * Use the interface index to set a zone on the source address, if the
         * source address has a scope.
         */
        if (ip6_addr_has_scope(ip_2_ip6(&ipaddr), IP6_UNKNOWN)) {
                if (ifindex == 0)
                        return EADDRNOTAVAIL;

                ip6_addr_set_zone(ip_2_ip6(&ipaddr), ifindex);
        }

        /*
         * We need to validate the given address just as thoroughly as an
         * address given through bind().  If we don't, we could allow forged
         * source addresses etcetera.  To be sure: this call may change the
         * address to an IPv4 type address if needed.
         */
        if ((r = ipsock_check_src_addr(pktsock_get_ipsock(pkt), &ipaddr,
            FALSE /*allow_mcast*/, &ifdev2)) != OK)
                return r;

        if (ifdev2 != NULL) {
                if (ifdev == NULL)
                        ifdev = ifdev2;
                else if (ifdev != ifdev2)
                        return EADDRNOTAVAIL;
        } else {
                /*
                 * There should be no cases where the (non-multicast) address
                 * successfully parsed, is not unspecified, and yet did not map
                 * to an interface.  Eliminate the possibility anyway by
                 * throwing an error for this case.  As a result, we are left
                 * with one of two cases:
                 *
                 * 1) ifdevp is not NULL, and src_addrp is unspecified;
                 * 2) ifdevp is not NULL, and src_addrp is a locally assigned
                 *    (unicast) address.
                 *
                 * This is why we need not fill src_addrp when ifdevp is NULL.
                 */
                if (!ip_addr_isany(&ipaddr))
                        return EADDRNOTAVAIL;
        }

        *ifdevp = ifdev;
        if (ifdev != NULL)
                *src_addrp = ipaddr;
        return OK;
}

/*
 * Parse a chunk of user-provided control data, on an IPv4 socket provided as
 * 'pkt'.  The control chunk is given as 'cmsg', and the length of the data
 * following the control header (possibly zero) is given as 'len'.  On success,
 * return OK, with any parsed options merged into the set of packet options
 * 'pkto'.  On failure, return a negative error code.
 */
static int
pktsock_parse_ctl_v4(struct pktsock * pkt __unused, struct cmsghdr * cmsg,
        socklen_t len, struct pktopt * pkto)
{
        uint8_t byte;
        int val;

        if (cmsg->cmsg_level != IPPROTO_IP)
                return EAFNOSUPPORT;

        switch (cmsg->cmsg_type) {
        case IP_TOS:
                /*
                 * Some userland code (bind's libisc in particular) supplies
                 * a single byte instead of a full integer for this option.
                 * We go out of our way to accept that format, too.
                 */
                if (len != sizeof(val) && len != sizeof(byte))
                        return EINVAL;

                if (len == sizeof(byte)) {
                        memcpy(&byte, CMSG_DATA(cmsg), sizeof(byte));
                        val = (int)byte;
                } else
                        memcpy(&val, CMSG_DATA(cmsg), sizeof(val));

                if (val < 0 || val > UINT8_MAX)
                        return EINVAL;

                pkto->pkto_flags |= PKTOF_TOS;
                pkto->pkto_tos = (uint8_t)val;

                return OK;

        case IP_TTL:
                if (len != sizeof(val))
                        return EINVAL;

                memcpy(&val, CMSG_DATA(cmsg), sizeof(val));

                if (val < 0 || val > UINT8_MAX)
                        return EINVAL;

                pkto->pkto_flags |= PKTOF_TTL;
                pkto->pkto_ttl = (uint8_t)val;

                return OK;

        /*
         * Implementing IP_PKTINFO might be a bit harder than its IPV6_PKTINFO
         * sibling, because it would require the use of zone IDs (interface
         * indices) for IPv4, which is not supported yet.
         */
        }

        return EINVAL;
}

/*
 * Parse a chunk of user-provided control data, on an IPv6 socket provided as
 * 'pkt'.  The control chunk is given as 'cmsg', and the length of the data
 * following the control header (possibly zero) is given as 'len'.  On success,
 * return OK, with any parsed options merged into the set of packet options
 * 'pkto'.  On failure, return a negative error code.
 */
static int
pktsock_parse_ctl_v6(struct pktsock * pkt, struct cmsghdr * cmsg,
        socklen_t len, struct pktopt * pkto)
{
        struct in6_pktinfo ipi6;
        int val;

        if (cmsg->cmsg_level != IPPROTO_IPV6)
                return EAFNOSUPPORT;

        switch (cmsg->cmsg_type) {
        case IPV6_TCLASS:
                if (len != sizeof(val))
                        return EINVAL;

                memcpy(&val, CMSG_DATA(cmsg), sizeof(val));

                if (val < -1 || val > UINT8_MAX)
                        return EINVAL;

                if (val == -1)
                        val = 0;

                pkto->pkto_flags |= PKTOF_TOS;
                pkto->pkto_tos = (uint8_t)val;

                return OK;

        case IPV6_HOPLIMIT:
                if (len != sizeof(val))
                        return EINVAL;

                memcpy(&val, CMSG_DATA(cmsg), sizeof(val));

                if (val < -1 || val > UINT8_MAX)
                        return EINVAL;

                if (val == -1)
                        val = IP_DEFAULT_TTL;

                pkto->pkto_flags |= PKTOF_TTL;
                pkto->pkto_ttl = (uint8_t)val;

                return OK;

        case IPV6_PKTINFO:
                if (len != sizeof(ipi6))
                        return EINVAL;

                memcpy(&ipi6, CMSG_DATA(cmsg), sizeof(ipi6));

                pkto->pkto_flags |= PKTOF_PKTINFO;
                memcpy(&pkto->pkto_srcaddr.addr, &ipi6.ipi6_addr,
                    sizeof(pkto->pkto_srcaddr.addr));
                pkto->pkto_ifindex = ipi6.ipi6_ifindex;

                return OK;

        case IPV6_USE_MIN_MTU:
                if (len != sizeof(int))
                        return EINVAL;

                memcpy(&val, CMSG_DATA(cmsg), sizeof(val));

                if (val < -1 || val > 1)
                        return EINVAL;

                /* TODO: not supported by lwIP, but needed by applications. */
                return OK;
        }

        return EINVAL;
}

/*
 * Copy in and parse control data, as part of sending a packet on socket 'pkt'.
 * The control data is accessible through 'ctl', with a user-provided length of
 * 'ctl_len'.  On success, return OK, with any parsed packet options stored in
 * 'pkto'.  On failure, return a negative error code.
 */
int
pktsock_get_ctl(struct pktsock * pkt, const struct sockdriver_data * ctl,
        socklen_t ctl_len, struct pktopt * pkto)
{
        struct msghdr msghdr;
        struct cmsghdr *cmsg;
        socklen_t left, len;
        int r;

        /* The default: no packet options are being overridden. */
        assert(pkto->pkto_flags == 0);

        /* If no control length is given, we are done here. */
        if (ctl_len == 0)
                return OK;

        /*
         * For now, we put a rather aggressive limit on the size of the control
         * data.  We copy in and parse the whole thing in a single buffer.
         */
        if (ctl_len > sizeof(pktsock_ctlbuf)) {
                printf("LWIP: too much control data given (%u bytes)\n",
                    ctl_len);

                return ENOBUFS;
        }

        if ((r = sockdriver_copyin(ctl, 0, pktsock_ctlbuf, ctl_len)) != OK)
                return r;

        memset(&msghdr, 0, sizeof(msghdr));
        msghdr.msg_control = pktsock_ctlbuf;
        msghdr.msg_controllen = ctl_len;

        for (cmsg = CMSG_FIRSTHDR(&msghdr); cmsg != NULL;
            cmsg = CMSG_NXTHDR(&msghdr, cmsg)) {
                /* Check for bogus lengths. */
                assert((socklen_t)((char *)cmsg - pktsock_ctlbuf) <= ctl_len);
                left = ctl_len - (socklen_t)((char *)cmsg - pktsock_ctlbuf);
                assert(left >= CMSG_LEN(0)); /* guaranteed by CMSG_xxHDR */

                if (cmsg->cmsg_len < CMSG_LEN(0) || cmsg->cmsg_len > left) {
                        printf("LWIP: malformed control data rejected\n");

                        return EINVAL;
                }

                len = cmsg->cmsg_len - CMSG_LEN(0);

                if (ipsock_is_ipv6(&pkt->pkt_ipsock))
                        r = pktsock_parse_ctl_v6(pkt, cmsg, len, pkto);
                else
                        r = pktsock_parse_ctl_v4(pkt, cmsg, len, pkto);

                if (r != OK)
                        return r;
        }

        return OK;
}

/*
 * Copy in the packet data from the calling user process, and store it in the
 * buffer 'pbuf' that must already have been allocated with the appropriate
 * size.
 */
int
pktsock_get_data(struct pktsock * pkt, const struct sockdriver_data * data,
        size_t len, struct pbuf * pbuf)

{

        return util_copy_data(data, len, 0, pbuf, 0, TRUE /*copy_in*/);
}

/*
 * Dequeue and free the head of the receive queue of a packet socket.
 */
static void
pktsock_dequeue(struct pktsock * pkt)
{
        struct pbuf *pbuf, **pnext;
        size_t size;

        pbuf = pkt->pkt_rcvhead;
        assert(pbuf != NULL);

        pnext = pchain_end(pbuf);
        size = pchain_size(pbuf);

        if ((pkt->pkt_rcvhead = *pnext) == NULL)
                pkt->pkt_rcvtailp = &pkt->pkt_rcvhead;

        assert(pkt->pkt_rcvlen >= size);
        pkt->pkt_rcvlen -= size;

        *pnext = NULL;
        pbuf_free(pbuf);
}

/*
 * Perform preliminary checks on a receive request.
 */
int
pktsock_pre_recv(struct sock * sock __unused, endpoint_t user_endpt __unused,
        int flags)
{

        /*
         * We accept the same flags across all socket types in LWIP, and then
         * simply ignore the ones we do not support for packet sockets.
         */
        if ((flags & ~(MSG_PEEK | MSG_WAITALL)) != 0)
                return EOPNOTSUPP;

        return OK;
}

/*
 * Add a chunk of control data to the global control buffer, starting from
 * offset 'off'.  The chunk has the given level and type, and its data is given
 * in the buffer 'ptr' with size 'len'.  Return the (padded) size of the chunk
 * that was generated as a result.
 */
static size_t
pktsock_add_ctl(int level, int type, void * ptr, socklen_t len, size_t off)
{
        struct cmsghdr cmsg;
        size_t size;

        size = CMSG_SPACE(len);

        /*
         * The global control buffer must be large enough to store one chunk
         * of each of the supported options.  If this panic triggers, increase
         * PKTSOCK_CTLBUF_SIZE by as much as needed.
         */
        if (off + size > sizeof(pktsock_ctlbuf))
                panic("control buffer too small, increase "
                    "PKTSOCK_CTLBUF_SIZE");

        memset(&cmsg, 0, sizeof(cmsg));
        cmsg.cmsg_len = CMSG_LEN(len);
        cmsg.cmsg_level = level;
        cmsg.cmsg_type = type;

        /*
         * Clear any padding space.  This can be optimized, but in any case we
         * must be careful not to copy out any bytes that have not been
         * initialized at all.
         */
        memset(&pktsock_ctlbuf[off], 0, size);

        memcpy(&pktsock_ctlbuf[off], &cmsg, sizeof(cmsg));
        memcpy(CMSG_DATA((struct cmsghdr *)&pktsock_ctlbuf[off]), ptr, len);

        return size;
}

/*
 * Generate and copy out control data, as part of delivering a packet from
 * socket 'pkt' to userland.  The control data buffer is given as 'ctl', with
 * a user-given length of 'ctl_len' bytes.  The packet's header information is
 * provided as 'pkthdr', and its source and destination addresses as 'pktaddr',
 * which maybe a pktaddr4 or pktaddr6 structure depending on the value of the
 * PKTHF_IPV6 flag in the 'flags' field in 'pkthdr'.  Note that we support
 * dual-stack sockets, and as such it is possible that the socket is of domain
 * AF_INET6 while the received packet is an IPv4 packet.  On success, return
 * the size of the control data copied out (possibly zero).  If more control
 * data were generated than copied out, also merge the MSG_CTRUNC flag into
 * 'rflags'.  On failure, return a negative error code.
 */
static int
pktsock_put_ctl(struct pktsock * pkt, const struct sockdriver_data * ctl,
        socklen_t ctl_len, struct pkthdr * pkthdr, void * pktaddr,
        int * rflags)
{
        struct pktaddr6 *pktaddr6;
        struct pktaddr4 *pktaddr4;
        struct in_pktinfo ipi;
        struct in6_pktinfo ipi6;
        ip_addr_t ipaddr;
        unsigned int flags;
        uint8_t byte;
        size_t off;
        int r, val;

        flags = ipsock_get_flags(&pkt->pkt_ipsock);

        if (!(flags & (PKTF_RECVINFO | PKTF_RECVTOS | PKTF_RECVTTL)))
                return 0;

        /*
         * Important: all generated control chunks must fit in the global
         * control buffer together.  When adding more options here, ensure that
         * the control buffer remains large enough to receive all options at
         * once.  See also the panic in pktsock_add_ctl().
         */
        off = 0;

        /*
         * IPv6 sockets may receive IPv4 packets.  The ancillary data is in the
         * format corresponding to the socket, which means we may have to
         * convert any IPv4 addresses from the packet to IPv4-mapped IPv6
         * addresses for the ancillary data, just like the source address.
         */
        if (ipsock_is_ipv6(&pkt->pkt_ipsock)) {
                if (flags & PKTF_RECVTTL) {
                        val = pkthdr->ttl;

                        off += pktsock_add_ctl(IPPROTO_IPV6, IPV6_HOPLIMIT,
                            &val, sizeof(val), off);
                }

                if (flags & PKTF_RECVTOS) {
                        val = pkthdr->tos;

                        off += pktsock_add_ctl(IPPROTO_IPV6, IPV6_TCLASS, &val,
                            sizeof(val), off);
                }

                if (flags & PKTF_RECVINFO) {
                        memset(&ipi6, 0, sizeof(ipi6));

                        if (pkthdr->flags & PKTHF_IPV6) {
                                pktaddr6 = (struct pktaddr6 *)pktaddr;
                                memcpy(&ipi6.ipi6_addr, &pktaddr6->dstaddr,
                                    sizeof(ipi6.ipi6_addr));
                        } else {
                                pktaddr4 = (struct pktaddr4 *)pktaddr;

                                addr_make_v4mapped_v6(&ipaddr,
                                    &pktaddr4->dstaddr);

                                memcpy(&ipi6.ipi6_addr,
                                    ip_2_ip6(&ipaddr)->addr,
                                    sizeof(ipi6.ipi6_addr));
                        }
                        ipi6.ipi6_ifindex = pkthdr->dstif;

                        off += pktsock_add_ctl(IPPROTO_IPV6, IPV6_PKTINFO,
                            &ipi6, sizeof(ipi6), off);
                }
        } else {
                if (flags & PKTF_RECVTTL) {
                        byte = pkthdr->ttl;

                        off += pktsock_add_ctl(IPPROTO_IP, IP_TTL, &byte,
                            sizeof(byte), off);
                }

                if (flags & PKTF_RECVINFO) {
                        assert(!(pkthdr->flags & PKTHF_IPV6));
                        pktaddr4 = (struct pktaddr4 *)pktaddr;

                        memset(&ipi, 0, sizeof(ipi));
                        memcpy(&ipi.ipi_addr, &pktaddr4->dstaddr,
                            sizeof(ipi.ipi_addr));
                        ipi.ipi_ifindex = pkthdr->dstif;

                        off += pktsock_add_ctl(IPPROTO_IP, IP_PKTINFO, &ipi,
                            sizeof(ipi), off);
                }
        }

        assert(off > 0);

        if (ctl_len >= off)
                ctl_len = off;
        else
                *rflags |= MSG_CTRUNC;

        if (ctl_len > 0 &&
            (r = sockdriver_copyout(ctl, 0, pktsock_ctlbuf, ctl_len)) != OK)
                return r;

        return ctl_len;
}

/*
 * Receive data on a packet socket.
 */
int
pktsock_recv(struct sock * sock, const struct sockdriver_data * data,
        size_t len, size_t * off, const struct sockdriver_data * ctl,
        socklen_t ctl_len, socklen_t * ctl_off, struct sockaddr * addr,
        socklen_t * addr_len, endpoint_t user_endpt __unused, int flags,
        size_t min __unused, int * rflags)
{
        struct pktsock *pkt = (struct pktsock *)sock;
        struct pktaddr4 pktaddr4;
        struct pktaddr6 pktaddr6;
        struct pkthdr pkthdr;
        void *pktaddr;
        struct pbuf *pbuf;
        ip_addr_t srcaddr;
        int r;

        if ((pbuf = pkt->pkt_rcvhead) == NULL)
                return SUSPEND;

        /*
         * Get the ancillary data for the packet.  The format of the ancillary
         * data depends on the received packet type, which may be different
         * from the socket type.
         */
        util_pbuf_header(pbuf, sizeof(pkthdr));

        memcpy(&pkthdr, pbuf->payload, sizeof(pkthdr));

        if (pkthdr.flags & PKTHF_IPV6) {
                util_pbuf_header(pbuf, sizeof(pktaddr6));

                memcpy(&pktaddr6, pbuf->payload, sizeof(pktaddr6));
                pktaddr = &pktaddr6;

                ip_addr_copy_from_ip6_packed(srcaddr, pktaddr6.srcaddr);
                if (ip6_addr_has_scope(ip_2_ip6(&srcaddr), IP6_UNICAST))
                        ip6_addr_set_zone(ip_2_ip6(&srcaddr), pkthdr.addrif);

                util_pbuf_header(pbuf,
                    -(int)(sizeof(pkthdr) + sizeof(pktaddr6)));
        } else {
                util_pbuf_header(pbuf, sizeof(pktaddr4));

                memcpy(&pktaddr4, pbuf->payload, sizeof(pktaddr4));
                pktaddr = &pktaddr4;

                ip_addr_copy_from_ip4(srcaddr, pktaddr4.srcaddr);

                util_pbuf_header(pbuf,
                    -(int)(sizeof(pkthdr) + sizeof(pktaddr4)));
        }

        /* Copy out the packet data to the calling user process. */
        if (len >= pbuf->tot_len)
                len = pbuf->tot_len;
        else
                *rflags |= MSG_TRUNC;

        r = util_copy_data(data, len, 0, pbuf, 0, FALSE /*copy_in*/);

        if (r != OK)
                return r;

        /* Generate and copy out ancillary (control) data, if requested. */
        if ((r = pktsock_put_ctl(pkt, ctl, ctl_len, &pkthdr, pktaddr,
            rflags)) < 0)
                return r;

        /* Store the source IP address. */
        ipsock_put_addr(&pkt->pkt_ipsock, addr, addr_len, &srcaddr,
            pkthdr.port);

        /* Set multicast or broadcast message flag, if applicable. */
        if (pkthdr.flags & PKTHF_MCAST)
                *rflags |= MSG_MCAST;
        else if (pkthdr.flags & PKTHF_BCAST)
                *rflags |= MSG_BCAST;

        /* Discard the packet now, unless we were instructed to peek only. */
        if (!(flags & MSG_PEEK))
                pktsock_dequeue(pkt);

        /* Return the received part of the packet length. */
        *off = len;
        *ctl_off = r;
        return OK;
}

/*
 * Test whether data can be received on a packet socket, and if so, how many
 * bytes of data.
 */
int
pktsock_test_recv(struct sock * sock, size_t min __unused, size_t * size)
{
        struct pktsock *pkt = (struct pktsock *)sock;

        if (pkt->pkt_rcvhead == NULL)
                return SUSPEND;

        if (size != NULL)
                *size = pkt->pkt_rcvhead->tot_len;
        return OK;
}

/*
 * The caller has performed a multicast operation on the given socket.  Thus,
 * the caller is multicast aware.  Remember this, because that means the socket
 * may also receive traffic to multicast destinations.
 */
void
pktsock_set_mcaware(struct pktsock * pkt)
{

        ipsock_set_flag(&pkt->pkt_ipsock, PKTF_MCAWARE);
}

/*
 * Set socket options on a packet socket.
 */
int
pktsock_setsockopt(struct pktsock * pkt, int level, int name,
        const struct sockdriver_data * data, socklen_t len,
        struct ipopts * ipopts)
{
        struct ip_mreq imr;
        struct ipv6_mreq ipv6mr;
        struct in6_pktinfo ipi6;
        ip_addr_t ipaddr, ifaddr;
        struct ifdev *ifdev;
        unsigned int flag;
        uint32_t ifindex;
        int r, val, has_scope;

        switch (level) {
        case IPPROTO_IP:
                if (ipsock_is_ipv6(&pkt->pkt_ipsock))
                        break;

                switch (name) {
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                        pktsock_set_mcaware(pkt);

                        if ((r = sockdriver_copyin_opt(data, &imr, sizeof(imr),
                            len)) != OK)
                                return r;

                        ip_addr_set_ip4_u32(&ipaddr, imr.imr_multiaddr.s_addr);
                        ip_addr_set_ip4_u32(&ifaddr, imr.imr_interface.s_addr);

                        if (!ip_addr_isany(&ifaddr)) {
                                ifdev = ifaddr_map_by_addr(&ifaddr);

                                if (ifdev == NULL)
                                        return EADDRNOTAVAIL;
                        } else
                                ifdev = NULL;

                        if (name == IP_ADD_MEMBERSHIP)
                                r = mcast_join(&pkt->pkt_mcast, &ipaddr,
                                    ifdev);
                        else
                                r = mcast_leave(&pkt->pkt_mcast, &ipaddr,
                                    ifdev);

                        return r;

                case IP_RECVTTL:
                case IP_RECVPKTINFO:
                        if ((r = sockdriver_copyin_opt(data, &val, sizeof(val),
                            len)) != OK)
                                return r;

                        switch (name) {
                        case IP_RECVTTL:        flag = PKTF_RECVTTL; break;
                        case IP_RECVPKTINFO:    flag = PKTF_RECVINFO; break;
                        default:                flag = 0; assert(0); break;
                        }

                        if (val)
                                ipsock_set_flag(&pkt->pkt_ipsock, flag);
                        else
                                ipsock_clear_flag(&pkt->pkt_ipsock, flag);

                        return OK;
                }

                break;

        case IPPROTO_IPV6:
                if (!ipsock_is_ipv6(&pkt->pkt_ipsock))
                        break;

                switch (name) {
                case IPV6_JOIN_GROUP:
                case IPV6_LEAVE_GROUP:
                        pktsock_set_mcaware(pkt);

                        if ((r = sockdriver_copyin_opt(data, &ipv6mr,
                            sizeof(ipv6mr), len)) != OK)
                                return r;

                        ip_addr_set_zero_ip6(&ipaddr);
                        memcpy(ip_2_ip6(&ipaddr)->addr,
                            &ipv6mr.ipv6mr_multiaddr,
                            sizeof(ip_2_ip6(&ipaddr)->addr));

                        /*
                         * We currently do not support joining IPv4 multicast
                         * groups on IPv6 sockets.  The reason for this is that
                         * this would require decisions on what to do if the
                         * socket is set to V6ONLY later, as well as various
                         * additional exceptions for a case that hopefully
                         * doesn't occur in practice anyway.
                         */
                        if (ip6_addr_isipv4mappedipv6(ip_2_ip6(&ipaddr)))
                                return EADDRNOTAVAIL;

                        has_scope = ip6_addr_has_scope(ip_2_ip6(&ipaddr),
                            IP6_UNKNOWN);

                        if ((ifindex = ipv6mr.ipv6mr_interface) != 0) {
                                ifdev = ifdev_get_by_index(ifindex);

                                if (ifdev == NULL)
                                        return ENXIO;

                                if (has_scope)
                                        ip6_addr_set_zone(ip_2_ip6(&ipaddr),
                                            ifindex);
                        } else {
                                if (has_scope)
                                        return EADDRNOTAVAIL;

                                ifdev = NULL;
                        }

                        if (name == IPV6_JOIN_GROUP)
                                r = mcast_join(&pkt->pkt_mcast, &ipaddr,
                                    ifdev);
                        else
                                r = mcast_leave(&pkt->pkt_mcast, &ipaddr,
                                    ifdev);

                        return r;

                case IPV6_USE_MIN_MTU:
                        if ((r = sockdriver_copyin_opt(data, &val, sizeof(val),
                            len)) != OK)
                                return r;

                        if (val < -1 || val > 1)
                                return EINVAL;

                        /*
                         * lwIP does not support path MTU discovery, so do
                         * nothing.  TODO: see if this is actually good enough.
                         */
                        return OK;

                case IPV6_PKTINFO:
                        if ((r = sockdriver_copyin_opt(data, &ipi6,
                            sizeof(ipi6), len)) != OK)
                                return r;

                        /*
                         * Simply copy in what is given.  The values will be
                         * parsed only once a packet is sent, in
                         * pktsock_get_pktinfo().  Otherwise, if we perform
                         * checks here, they may be outdated by the time the
                         * values are actually used.
                         */
                        memcpy(&pkt->pkt_srcaddr.addr, &ipi6.ipi6_addr,
                            sizeof(pkt->pkt_srcaddr.addr));
                        pkt->pkt_ifindex = ipi6.ipi6_ifindex;

                        return OK;

                case IPV6_RECVPKTINFO:
                case IPV6_RECVHOPLIMIT:
                case IPV6_RECVTCLASS:
                        if ((r = sockdriver_copyin_opt(data, &val, sizeof(val),
                            len)) != OK)
                                return r;

                        switch (name) {
                        case IPV6_RECVPKTINFO:  flag = PKTF_RECVINFO; break;
                        case IPV6_RECVHOPLIMIT: flag = PKTF_RECVTTL; break;
                        case IPV6_RECVTCLASS:   flag = PKTF_RECVTOS; break;
                        default:                flag = 0; assert(0); break;
                        }

                        if (val)
                                ipsock_set_flag(&pkt->pkt_ipsock, flag);
                        else
                                ipsock_clear_flag(&pkt->pkt_ipsock, flag);

                        return OK;
                }

                break;
        }

        return ipsock_setsockopt(&pkt->pkt_ipsock, level, name, data, len,
            ipopts);
}

/*
 * Retrieve socket options on a packet socket.
 */
int
pktsock_getsockopt(struct pktsock * pkt, int level, int name,
        const struct sockdriver_data * data, socklen_t * len,
        struct ipopts * ipopts)
{
        struct in6_pktinfo ipi6;
        unsigned int flag;
        int val;

        switch (level) {
        case IPPROTO_IP:
                if (ipsock_is_ipv6(&pkt->pkt_ipsock))
                        break;

                switch (name) {
                case IP_RECVTTL:
                case IP_RECVPKTINFO:
                        switch (name) {
                        case IP_RECVTTL:        flag = PKTF_RECVTTL; break;
                        case IP_RECVPKTINFO:    flag = PKTF_RECVINFO; break;
                        default:                flag = 0; assert(0); break;
                        }

                        val = !!(ipsock_get_flag(&pkt->pkt_ipsock, flag));

                        return sockdriver_copyout_opt(data, &val, sizeof(val),
                            len);
                }

                break;

        case IPPROTO_IPV6:
                if (!ipsock_is_ipv6(&pkt->pkt_ipsock))
                        break;

                switch (name) {
                case IPV6_USE_MIN_MTU:
                        /*
                         * TODO: sort out exactly what lwIP actually supports
                         * in the way of path MTU discovery.  Value 1 means
                         * that path MTU discovery is disabled and packets are
                         * sent at the minimum MTU (RFC 3542).
                         */
                        val = 1;

                        return sockdriver_copyout_opt(data, &val, sizeof(val),
                            len);

                case IPV6_PKTINFO:
                        memset(&ipi6, 0, sizeof(ipi6));

                        /*
                         * Simply copy out whatever was given before.  These
                         * fields are initialized to zero on socket creation.
                         */
                        memcpy(&ipi6.ipi6_addr, &pkt->pkt_srcaddr.addr,
                            sizeof(ipi6.ipi6_addr));
                        ipi6.ipi6_ifindex = pkt->pkt_ifindex;

                        return sockdriver_copyout_opt(data, &ipi6,
                            sizeof(ipi6), len);

                case IPV6_RECVPKTINFO:
                case IPV6_RECVHOPLIMIT:
                case IPV6_RECVTCLASS:
                        switch (name) {
                        case IPV6_RECVPKTINFO:  flag = PKTF_RECVINFO; break;
                        case IPV6_RECVHOPLIMIT: flag = PKTF_RECVTTL; break;
                        case IPV6_RECVTCLASS:   flag = PKTF_RECVTOS; break;
                        default:                flag = 0; assert(0); break;
                        }

                        val = !!(ipsock_get_flag(&pkt->pkt_ipsock, flag));

                        return sockdriver_copyout_opt(data, &val, sizeof(val),
                            len);
                }

                break;
        }

        return ipsock_getsockopt(&pkt->pkt_ipsock, level, name, data, len,
            ipopts);
}

/*
 * Drain the receive queue of a packet socket.
 */
static void
pktsock_drain(struct pktsock * pkt)
{

        while (pkt->pkt_rcvhead != NULL)
                pktsock_dequeue(pkt);

        assert(pkt->pkt_rcvlen == 0);
        assert(pkt->pkt_rcvtailp == &pkt->pkt_rcvhead);
}

/*
 * Shut down a packet socket for reading and/or writing.
 */
void
pktsock_shutdown(struct pktsock * pkt, unsigned int mask)
{

        if (mask & SFL_SHUT_RD)
                pktsock_drain(pkt);
}

/*
 * Close a packet socket.
 */
void
pktsock_close(struct pktsock * pkt)
{

        pktsock_drain(pkt);

        mcast_leave_all(&pkt->pkt_mcast);
}

/*
 * Return the rounded-up number of bytes in the packet socket's receive queue,
 * for sysctl(7).  NetBSD returns the used portion of each buffer, but that
 * would be quite some extra effort for us (TODO).
 */
size_t
pktsock_get_recvlen(struct pktsock * pkt)
{

        return pkt->pkt_rcvlen;
}