actions.c

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/*
 * Copyright (c) 2007-2012 Nicira, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/openvswitch.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/in6.h>
#include <linux/if_arp.h>
#include <linux/if_vlan.h>
#include <net/ip.h>
#include <net/checksum.h>
#include <net/dsfield.h>

#include "datapath.h"
#include "vport.h"

static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
            const struct nlattr *attr, int len, bool keep_skb);

static int make_writable(struct sk_buff *skb, int write_len)
{
    if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
        return 0;

    return pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
}

/* remove VLAN header from packet and update csum accordingly. */
static int __pop_vlan_tci(struct sk_buff *skb, __be16 *current_tci)
{
    struct vlan_hdr *vhdr;
    int err;

    err = make_writable(skb, VLAN_ETH_HLEN);
    if (unlikely(err))
        return err;

    if (skb->ip_summed == CHECKSUM_COMPLETE)
        skb->csum = csum_sub(skb->csum, csum_partial(skb->data
                    + ETH_HLEN, VLAN_HLEN, 0));

    vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
    *current_tci = vhdr->h_vlan_TCI;

    memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);
    __skb_pull(skb, VLAN_HLEN);

    vlan_set_encap_proto(skb, vhdr);
    skb->mac_header += VLAN_HLEN;
    skb_reset_mac_len(skb);

    return 0;
}

static int pop_vlan(struct sk_buff *skb)
{
    __be16 tci;
    int err;

    if (likely(vlan_tx_tag_present(skb))) {
        skb->vlan_tci = 0;
    } else {
        if (unlikely(skb->protocol != htons(ETH_P_8021Q) ||
                 skb->len < VLAN_ETH_HLEN))
            return 0;

        err = __pop_vlan_tci(skb, &tci);
        if (err)
            return err;
    }
    /* move next vlan tag to hw accel tag */
    if (likely(skb->protocol != htons(ETH_P_8021Q) ||
           skb->len < VLAN_ETH_HLEN))
        return 0;

    err = __pop_vlan_tci(skb, &tci);
    if (unlikely(err))
        return err;

    __vlan_hwaccel_put_tag(skb, ntohs(tci));
    return 0;
}

static int push_vlan(struct sk_buff *skb, const struct ovs_action_push_vlan *vlan)
{
    if (unlikely(vlan_tx_tag_present(skb))) {
        u16 current_tag;

        /* push down current VLAN tag */
        current_tag = vlan_tx_tag_get(skb);

        if (!__vlan_put_tag(skb, current_tag))
            return -ENOMEM;

        if (skb->ip_summed == CHECKSUM_COMPLETE)
            skb->csum = csum_add(skb->csum, csum_partial(skb->data
                    + ETH_HLEN, VLAN_HLEN, 0));

    }
    __vlan_hwaccel_put_tag(skb, ntohs(vlan->vlan_tci) & ~VLAN_TAG_PRESENT);
    return 0;
}

static int set_eth_addr(struct sk_buff *skb,
            const struct ovs_key_ethernet *eth_key)
{
    int err;
    err = make_writable(skb, ETH_HLEN);
    if (unlikely(err))
        return err;

    memcpy(eth_hdr(skb)->h_source, eth_key->eth_src, ETH_ALEN);
    memcpy(eth_hdr(skb)->h_dest, eth_key->eth_dst, ETH_ALEN);

    return 0;
}

static void set_ip_addr(struct sk_buff *skb, struct iphdr *nh,
                __be32 *addr, __be32 new_addr)
{
    int transport_len = skb->len - skb_transport_offset(skb);

    if (nh->protocol == IPPROTO_TCP) {
        if (likely(transport_len >= sizeof(struct tcphdr)))
            inet_proto_csum_replace4(&tcp_hdr(skb)->check, skb,
                         *addr, new_addr, 1);
    } else if (nh->protocol == IPPROTO_UDP) {
        if (likely(transport_len >= sizeof(struct udphdr))) {
            struct udphdr *uh = udp_hdr(skb);

            if (uh->check || skb->ip_summed == CHECKSUM_PARTIAL) {
                inet_proto_csum_replace4(&uh->check, skb,
                             *addr, new_addr, 1);
                if (!uh->check)
                    uh->check = CSUM_MANGLED_0;
            }
        }
    }

    csum_replace4(&nh->check, *addr, new_addr);
    skb->rxhash = 0;
    *addr = new_addr;
}

static void set_ip_ttl(struct sk_buff *skb, struct iphdr *nh, u8 new_ttl)
{
    csum_replace2(&nh->check, htons(nh->ttl << 8), htons(new_ttl << 8));
    nh->ttl = new_ttl;
}

static int set_ipv4(struct sk_buff *skb, const struct ovs_key_ipv4 *ipv4_key)
{
    struct iphdr *nh;
    int err;

    err = make_writable(skb, skb_network_offset(skb) +
                 sizeof(struct iphdr));
    if (unlikely(err))
        return err;

    nh = ip_hdr(skb);

    if (ipv4_key->ipv4_src != nh->saddr)
        set_ip_addr(skb, nh, &nh->saddr, ipv4_key->ipv4_src);

    if (ipv4_key->ipv4_dst != nh->daddr)
        set_ip_addr(skb, nh, &nh->daddr, ipv4_key->ipv4_dst);

    if (ipv4_key->ipv4_tos != nh->tos)
        ipv4_change_dsfield(nh, 0, ipv4_key->ipv4_tos);

    if (ipv4_key->ipv4_ttl != nh->ttl)
        set_ip_ttl(skb, nh, ipv4_key->ipv4_ttl);

    return 0;
}

/* Must follow make_writable() since that can move the skb data. */
static void set_tp_port(struct sk_buff *skb, __be16 *port,
             __be16 new_port, __sum16 *check)
{
    inet_proto_csum_replace2(check, skb, *port, new_port, 0);
    *port = new_port;
    skb->rxhash = 0;
}

static void set_udp_port(struct sk_buff *skb, __be16 *port, __be16 new_port)
{
    struct udphdr *uh = udp_hdr(skb);

    if (uh->check && skb->ip_summed != CHECKSUM_PARTIAL) {
        set_tp_port(skb, port, new_port, &uh->check);

        if (!uh->check)
            uh->check = CSUM_MANGLED_0;
    } else {
        *port = new_port;
        skb->rxhash = 0;
    }
}

static int set_udp(struct sk_buff *skb, const struct ovs_key_udp *udp_port_key)
{
    struct udphdr *uh;
    int err;

    err = make_writable(skb, skb_transport_offset(skb) +
                 sizeof(struct udphdr));
    if (unlikely(err))
        return err;

    uh = udp_hdr(skb);
    if (udp_port_key->udp_src != uh->source)
        set_udp_port(skb, &uh->source, udp_port_key->udp_src);

    if (udp_port_key->udp_dst != uh->dest)
        set_udp_port(skb, &uh->dest, udp_port_key->udp_dst);

    return 0;
}

static int set_tcp(struct sk_buff *skb, const struct ovs_key_tcp *tcp_port_key)
{
    struct tcphdr *th;
    int err;

    err = make_writable(skb, skb_transport_offset(skb) +
                 sizeof(struct tcphdr));
    if (unlikely(err))
        return err;

    th = tcp_hdr(skb);
    if (tcp_port_key->tcp_src != th->source)
        set_tp_port(skb, &th->source, tcp_port_key->tcp_src, &th->check);

    if (tcp_port_key->tcp_dst != th->dest)
        set_tp_port(skb, &th->dest, tcp_port_key->tcp_dst, &th->check);

    return 0;
}

static int do_output(struct datapath *dp, struct sk_buff *skb, int out_port)
{
    struct vport *vport;

    if (unlikely(!skb))
        return -ENOMEM;

    vport = ovs_vport_rcu(dp, out_port);
    if (unlikely(!vport)) {
        kfree_skb(skb);
        return -ENODEV;
    }

    ovs_vport_send(vport, skb);
    return 0;
}

static int output_userspace(struct datapath *dp, struct sk_buff *skb,
                const struct nlattr *attr)
{
    struct dp_upcall_info upcall;
    const struct nlattr *a;
    int rem;

    upcall.cmd = OVS_PACKET_CMD_ACTION;
    upcall.key = &OVS_CB(skb)->flow->key;
    upcall.userdata = NULL;
    upcall.portid = 0;

    for (a = nla_data(attr), rem = nla_len(attr); rem > 0;
         a = nla_next(a, &rem)) {
        switch (nla_type(a)) {
        case OVS_USERSPACE_ATTR_USERDATA:
            upcall.userdata = a;
            break;

        case OVS_USERSPACE_ATTR_PID:
            upcall.portid = nla_get_u32(a);
            break;
        }
    }

    return ovs_dp_upcall(dp, skb, &upcall);
}

static int sample(struct datapath *dp, struct sk_buff *skb,
          const struct nlattr *attr)
{
    const struct nlattr *acts_list = NULL;
    const struct nlattr *a;
    int rem;

    for (a = nla_data(attr), rem = nla_len(attr); rem > 0;
         a = nla_next(a, &rem)) {
        switch (nla_type(a)) {
        case OVS_SAMPLE_ATTR_PROBABILITY:
            if (net_random() >= nla_get_u32(a))
                return 0;
            break;

        case OVS_SAMPLE_ATTR_ACTIONS:
            acts_list = a;
            break;
        }
    }

    return do_execute_actions(dp, skb, nla_data(acts_list),
                         nla_len(acts_list), true);
}

static int execute_set_action(struct sk_buff *skb,
                 const struct nlattr *nested_attr)
{
    int err = 0;

    switch (nla_type(nested_attr)) {
    case OVS_KEY_ATTR_PRIORITY:
        skb->priority = nla_get_u32(nested_attr);
        break;

    case OVS_KEY_ATTR_ETHERNET:
        err = set_eth_addr(skb, nla_data(nested_attr));
        break;

    case OVS_KEY_ATTR_IPV4:
        err = set_ipv4(skb, nla_data(nested_attr));
        break;

    case OVS_KEY_ATTR_TCP:
        err = set_tcp(skb, nla_data(nested_attr));
        break;

    case OVS_KEY_ATTR_UDP:
        err = set_udp(skb, nla_data(nested_attr));
        break;
    }

    return err;
}

/* Execute a list of actions against 'skb'. */
static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
            const struct nlattr *attr, int len, bool keep_skb)
{
    /* Every output action needs a separate clone of 'skb', but the common
     * case is just a single output action, so that doing a clone and
     * then freeing the original skbuff is wasteful.  So the following code
     * is slightly obscure just to avoid that. */
    int prev_port = -1;
    const struct nlattr *a;
    int rem;

    for (a = attr, rem = len; rem > 0;
         a = nla_next(a, &rem)) {
        int err = 0;

        if (prev_port != -1) {
            do_output(dp, skb_clone(skb, GFP_ATOMIC), prev_port);
            prev_port = -1;
        }

        switch (nla_type(a)) {
        case OVS_ACTION_ATTR_OUTPUT:
            prev_port = nla_get_u32(a);
            break;

        case OVS_ACTION_ATTR_USERSPACE:
            output_userspace(dp, skb, a);
            break;

        case OVS_ACTION_ATTR_PUSH_VLAN:
            err = push_vlan(skb, nla_data(a));
            if (unlikely(err)) /* skb already freed. */
                return err;
            break;

        case OVS_ACTION_ATTR_POP_VLAN:
            err = pop_vlan(skb);
            break;

        case OVS_ACTION_ATTR_SET:
            err = execute_set_action(skb, nla_data(a));
            break;

        case OVS_ACTION_ATTR_SAMPLE:
            err = sample(dp, skb, a);
            break;
        }

        if (unlikely(err)) {
            kfree_skb(skb);
            return err;
        }
    }

    if (prev_port != -1) {
        if (keep_skb)
            skb = skb_clone(skb, GFP_ATOMIC);

        do_output(dp, skb, prev_port);
    } else if (!keep_skb)
        consume_skb(skb);

    return 0;
}

/* Execute a list of actions against 'skb'. */
int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb)
{
    struct sw_flow_actions *acts = rcu_dereference(OVS_CB(skb)->flow->sf_acts);

    return do_execute_actions(dp, skb, acts->actions,
                     acts->actions_len, false);
}