C++ pskb_expand_head函数代码示例

static int rmnet_map_egress_handler(struct sk_buff *skb,
				    struct rmnet_port *port, u8 mux_id,
				    struct net_device *orig_dev)
{
	int required_headroom, additional_header_len;
	struct rmnet_map_header *map_header;

	additional_header_len = 0;
	required_headroom = sizeof(struct rmnet_map_header);

	if (port->data_format & RMNET_FLAGS_EGRESS_MAP_CKSUMV4) {
		additional_header_len = sizeof(struct rmnet_map_ul_csum_header);
		required_headroom += additional_header_len;
	}

	if (skb_headroom(skb) < required_headroom) {
		if (pskb_expand_head(skb, required_headroom, 0, GFP_ATOMIC))
			return -ENOMEM;
	}

	if (port->data_format & RMNET_FLAGS_EGRESS_MAP_CKSUMV4)
		rmnet_map_checksum_uplink_packet(skb, orig_dev);

	map_header = rmnet_map_add_map_header(skb, additional_header_len, 0);
	if (!map_header)
		return -ENOMEM;

	map_header->mux_id = mux_id;

	skb->protocol = htons(ETH_P_MAP);

	return 0;
}

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);
}

static int xfrm6_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
{
	int err = -EINVAL;
	const unsigned char *old_mac;

	if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPV6)
		goto out;
	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
		goto out;

	if (skb_cloned(skb) &&
	    (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
		goto out;

	if (x->props.flags & XFRM_STATE_DECAP_DSCP)
		ipv6_copy_dscp(ipv6_get_dsfield(ipv6_hdr(skb)),
			       ipipv6_hdr(skb));
	if (!(x->props.flags & XFRM_STATE_NOECN))
		ipip6_ecn_decapsulate(skb);

	old_mac = skb_mac_header(skb);
	skb_set_mac_header(skb, -skb->mac_len);
	memmove(skb_mac_header(skb), old_mac, skb->mac_len);
	skb_reset_network_header(skb);
	err = 0;

out:
	return err;
}

/**
 * tipc_l2_send_msg - send a TIPC packet out over an L2 interface
 * @skb: the packet to be sent
 * @b: the bearer through which the packet is to be sent
 * @dest: peer destination address
 */
int tipc_l2_send_msg(struct net *net, struct sk_buff *skb,
		     struct tipc_bearer *b, struct tipc_media_addr *dest)
{
	struct net_device *dev;
	int delta;
	void *tipc_ptr;

	dev = (struct net_device *)rcu_dereference_rtnl(b->media_ptr);
	if (!dev)
		return 0;

	/* Send RESET message even if bearer is detached from device */
	tipc_ptr = rcu_dereference_rtnl(dev->tipc_ptr);
	if (unlikely(!tipc_ptr && !msg_is_reset(buf_msg(skb))))
		goto drop;

	delta = dev->hard_header_len - skb_headroom(skb);
	if ((delta > 0) &&
	    pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC))
		goto drop;

	skb_reset_network_header(skb);
	skb->dev = dev;
	skb->protocol = htons(ETH_P_TIPC);
	dev_hard_header(skb, dev, ETH_P_TIPC, dest->value,
			dev->dev_addr, skb->len);
	dev_queue_xmit(skb);
	return 0;
drop:
	kfree_skb(skb);
	return 0;
}

/**
 * tipc_l2_send_msg - send a TIPC packet out over an L2 interface
 * @buf: the packet to be sent
 * @b_ptr: the bearer through which the packet is to be sent
 * @dest: peer destination address
 */
int tipc_l2_send_msg(struct sk_buff *buf, struct tipc_bearer *b,
		     struct tipc_media_addr *dest)
{
	struct sk_buff *clone;
	struct net_device *dev;
	int delta;

	dev = (struct net_device *)rcu_dereference_rtnl(b->media_ptr);
	if (!dev)
		return 0;

	clone = skb_clone(buf, GFP_ATOMIC);
	if (!clone)
		return 0;

	delta = dev->hard_header_len - skb_headroom(buf);
	if ((delta > 0) &&
	    pskb_expand_head(clone, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
		kfree_skb(clone);
		return 0;
	}

	skb_reset_network_header(clone);
	clone->dev = dev;
	clone->protocol = htons(ETH_P_TIPC);
	dev_hard_header(clone, dev, ETH_P_TIPC, dest->value,
			dev->dev_addr, clone->len);
	dev_queue_xmit(clone);
	return 0;
}

/*
 * Transmit a packet to the base station on behalf of the network stack
 *
 *
 * Returns: NETDEV_TX_OK (always, even in case of error)
 *
 * In case of error, we just drop it. Reasons:
 *
 *  - we add a hw header to each skb, and if the network stack
 *    retries, we have no way to know if that skb has it or not.
 *
 *  - network protocols have their own drop-recovery mechanisms
 *
 *  - there is not much else we can do
 *
 * If the device is idle, we need to wake it up; that is an operation
 * that will sleep. See i2400m_net_wake_tx() for details.
 */
static
netdev_tx_t i2400m_hard_start_xmit(struct sk_buff *skb,
					 struct net_device *net_dev)
{
	struct i2400m *i2400m = net_dev_to_i2400m(net_dev);
	struct device *dev = i2400m_dev(i2400m);
	int result = -1;

	d_fnstart(3, dev, "(skb %p net_dev %p)\n", skb, net_dev);

	if (skb_header_cloned(skb) && 
	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
		goto drop;

	if (i2400m->state == I2400M_SS_IDLE)
		result = i2400m_net_wake_tx(i2400m, net_dev, skb);
	else
		result = i2400m_net_tx(i2400m, net_dev, skb);
	if (result <  0) {
drop:
		net_dev->stats.tx_dropped++;
	} else {
		net_dev->stats.tx_packets++;
		net_dev->stats.tx_bytes += skb->len;
	}
	dev_kfree_skb(skb);
	d_fnend(3, dev, "(skb %p net_dev %p) = %d\n", skb, net_dev, result);
	return NETDEV_TX_OK;
}

/**
 * rmnet_map_egress_handler() - MAP egress handler
 * @skb:        Packet being sent
 * @config:     Physical endpoint configuration for the egress device
 * @ep:         logical endpoint configuration of the packet originator
 *              (e.g.. RmNet virtual network device)
 * @orig_dev:   The originator vnd device
 *
 * Called if and only if MAP is configured in the egress device's egress data
 * format. Will expand skb if there is insufficient headroom for MAP protocol.
 * Note: headroomexpansion will incur a performance penalty.
 *
 * Return:
 *      - 0 on success
 *      - 1 on failure
 */
static int rmnet_map_egress_handler(struct sk_buff *skb,
				    struct rmnet_phys_ep_conf_s *config,
				    struct rmnet_logical_ep_conf_s *ep,
				    struct net_device *orig_dev)
{
	int required_headroom, additional_header_length, ckresult;
	struct rmnet_map_header_s *map_header;

	additional_header_length = 0;

	required_headroom = sizeof(struct rmnet_map_header_s);
	if ((config->egress_data_format & RMNET_EGRESS_FORMAT_MAP_CKSUMV3) ||
	    (config->egress_data_format & RMNET_EGRESS_FORMAT_MAP_CKSUMV4)) {
		required_headroom +=
			sizeof(struct rmnet_map_ul_checksum_header_s);
		additional_header_length +=
			sizeof(struct rmnet_map_ul_checksum_header_s);
	}

	LOGD("headroom of %d bytes", required_headroom);

	if (skb_headroom(skb) < required_headroom) {
		if (pskb_expand_head(skb, required_headroom, 0, GFP_KERNEL)) {
			LOGD("Failed to add headroom of %d bytes",
			     required_headroom);
			return 1;
		}
	}

	if ((config->egress_data_format & RMNET_EGRESS_FORMAT_MAP_CKSUMV3) ||
	    (config->egress_data_format & RMNET_EGRESS_FORMAT_MAP_CKSUMV4)) {
		ckresult = rmnet_map_checksum_uplink_packet
				(skb, orig_dev, config->egress_data_format);
		trace_rmnet_map_checksum_uplink_packet(orig_dev, ckresult);
		rmnet_stats_ul_checksum(ckresult);
	}

	map_header = rmnet_map_add_map_header(skb, additional_header_length);

	if (!map_header) {
		LOGD("%s", "Failed to add MAP header to egress packet");
		return 1;
	}

	if (config->egress_data_format & RMNET_EGRESS_FORMAT_MUXING) {
		if (ep->mux_id == 0xff)
			map_header->mux_id = 0;
		else
			map_header->mux_id = ep->mux_id;
	}

	skb->protocol = htons(ETH_P_MAP);

	if (config->egress_data_format & RMNET_EGRESS_FORMAT_AGGREGATION) {
		rmnet_map_aggregate(skb, config);
		return RMNET_MAP_CONSUMED;
	}

	return RMNET_MAP_SUCCESS;
}

int nf_xfrm_me_harder(struct net *net, struct sk_buff *skb, unsigned int family)
{
	struct flowi fl;
	unsigned int hh_len;
	struct dst_entry *dst;
	int err;

	err = xfrm_decode_session(skb, &fl, family);
	if (err < 0)
		return err;

	dst = skb_dst(skb);
	if (dst->xfrm)
		dst = ((struct xfrm_dst *)dst)->route;
	dst_hold(dst);

	dst = xfrm_lookup(net, dst, &fl, skb->sk, 0);
	if (IS_ERR(dst))
		return PTR_ERR(dst);

	skb_dst_drop(skb);
	skb_dst_set(skb, dst);

	/* Change in oif may mean change in hh_len. */
	hh_len = skb_dst(skb)->dev->hard_header_len;
	if (skb_headroom(skb) < hh_len &&
	    pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
		return -ENOMEM;
	return 0;
}

static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a,
		     struct tcf_result *res)
{
	struct tcf_pedit *p = a->priv;
	int i, munged = 0;
	unsigned int off;

	if (skb_cloned(skb) &&
	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
		return p->tcf_action;

	off = skb_network_offset(skb);

	spin_lock(&p->tcf_lock);

	p->tcf_tm.lastuse = jiffies;

	if (p->tcfp_nkeys > 0) {
		struct tc_pedit_key *tkey = p->tcfp_keys;

		for (i = p->tcfp_nkeys; i > 0; i--, tkey++) {
			u32 *ptr, _data;
			int offset = tkey->off;

			if (tkey->offmask) {
				char *d, _d;

				d = skb_header_pointer(skb, off + tkey->at, 1,
						       &_d);
				if (!d)
					goto bad;
				offset += (*d & tkey->offmask) >> tkey->shift;
			}

			if (offset % 4) {
				pr_info("tc filter pedit"
					" offset must be on 32 bit boundaries\n");
				goto bad;
			}
			if (offset > 0 && offset > skb->len) {
				pr_info("tc filter pedit"
					" offset %d can't exceed pkt length %d\n",
				       offset, skb->len);
				goto bad;
			}

			ptr = skb_header_pointer(skb, off + offset, 4, &_data);
			if (!ptr)
				goto bad;
			/* just do it, baby */
			*ptr = ((*ptr & tkey->mask) ^ tkey->val);
			if (ptr == &_data)
				skb_store_bits(skb, off + offset, ptr, 4);
			munged++;
		}

		if (munged)
			skb->tc_verd = SET_TC_MUNGED(skb->tc_verd);
		goto done;
	} else

int ip_vs_make_skb_writable(struct sk_buff **pskb, int writable_len)
{
	struct sk_buff *skb = *pskb;

	/* skb is already used, better copy skb and its payload */
	if (unlikely(skb_shared(skb) || skb->sk))
		goto copy_skb;

	/* skb data is already used, copy it */
	if (unlikely(skb_cloned(skb)))
		goto copy_data;

	return pskb_may_pull(skb, writable_len);

  copy_data:
	if (unlikely(writable_len > skb->len))
		return 0;
	return !pskb_expand_head(skb, 0, 0, GFP_ATOMIC);

  copy_skb:
	if (unlikely(writable_len > skb->len))
		return 0;
	skb = skb_copy(skb, GFP_ATOMIC);
	if (!skb)
		return 0;
	BUG_ON(skb_is_nonlinear(skb));

	/* Rest of kernel will get very unhappy if we pass it a
	   suddenly-orphaned skbuff */
	if ((*pskb)->sk)
		skb_set_owner_w(skb, (*pskb)->sk);
	kfree_skb(*pskb);
	*pskb = skb;
	return 1;
}

static int bpf_dp_ctx_init(struct bpf_dp_context *ctx)
{
	struct ovs_key_ipv4_tunnel *tun_key = OVS_CB(ctx->skb)->tun_key;

	if (skb_headroom(ctx->skb) < 64) {
		if (pskb_expand_head(ctx->skb, 64, 0, GFP_ATOMIC))
			return -ENOMEM;
	}
	ctx->context.length = ctx->skb->len;
	ctx->context.vlan_tag = vlan_tx_tag_present(ctx->skb) ?
			vlan_tx_tag_get(ctx->skb) : 0;
	ctx->context.hw_csum = (ctx->skb->ip_summed == CHECKSUM_PARTIAL);
	if (tun_key) {
		ctx->context.tun_key.tun_id =
				be32_to_cpu(be64_get_low32(tun_key->tun_id));
		ctx->context.tun_key.src_ip = be32_to_cpu(tun_key->ipv4_src);
		ctx->context.tun_key.dst_ip = be32_to_cpu(tun_key->ipv4_dst);
		ctx->context.tun_key.tos = tun_key->ipv4_tos;
		ctx->context.tun_key.ttl = tun_key->ipv4_ttl;
	} else {
		memset(&ctx->context.tun_key, 0,
		       sizeof(struct bpf_ipv4_tun_key));
	}

	return 0;
}

static int rmnet_map_egress_handler(struct sk_buff *skb,
				    struct rmnet_port *port, u8 mux_id,
				    struct net_device *orig_dev)
{
	int required_headroom, additional_header_len;
	struct rmnet_map_header *map_header;

	additional_header_len = 0;
	required_headroom = sizeof(struct rmnet_map_header);

	if (skb_headroom(skb) < required_headroom) {
		if (pskb_expand_head(skb, required_headroom, 0, GFP_KERNEL))
			return RMNET_MAP_CONSUMED;
	}

	map_header = rmnet_map_add_map_header(skb, additional_header_len, 0);
	if (!map_header)
		return RMNET_MAP_CONSUMED;

	if (port->egress_data_format & RMNET_EGRESS_FORMAT_MUXING) {
		if (mux_id == 0xff)
			map_header->mux_id = 0;
		else
			map_header->mux_id = mux_id;
	}

	skb->protocol = htons(ETH_P_MAP);

	return RMNET_MAP_SUCCESS;
}

int ip_xfrm_me_harder(struct sk_buff *skb)
{
    struct flowi fl;
    unsigned int hh_len;
    struct dst_entry *dst;

    if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
        return 0;
    if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
        return -1;

    dst = skb->dst;
    if (dst->xfrm)
        dst = ((struct xfrm_dst *)dst)->route;
    dst_hold(dst);

    if (xfrm_lookup(&dst, &fl, skb->sk, 0) < 0)
        return -1;

    dst_release(skb->dst);
    skb->dst = dst;

    /* Change in oif may mean change in hh_len. */
    hh_len = skb->dst->dev->hard_header_len;
    if (skb_headroom(skb) < hh_len &&
        pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
        return -1;
    return 0;
}

static inline int ipsec_encap_rcv_esp(struct sk_buff *skb, int len)
{
    struct iphdr *iph;
    int iphlen;

    if (!pskb_may_pull(skb, sizeof(struct udphdr) + len))
    {
        return -1;
    }
    
    if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
    {
        return -1;
    }
    
    iph = skb->nh.iph;
    iphlen = iph->ihl << 2;
    iph->tot_len = htons(ntohs(iph->tot_len) - len);
    
    if (skb->len < iphlen + len) 
    {
        return -1;
    }
    
    skb->h.raw = skb_pull(skb, len);
    
    iph->protocol = IPPROTO_ESP;
    return 0;
}

/**
 * send_msg - send a TIPC message out over an InfiniBand interface
 */
static int send_msg(struct sk_buff *buf, struct tipc_bearer *tb_ptr,
                    struct tipc_media_addr *dest)
{
    struct sk_buff *clone;
    struct net_device *dev;
    int delta;

    clone = skb_clone(buf, GFP_ATOMIC);
    if (!clone)
        return 0;

    dev = ((struct ib_bearer *)(tb_ptr->usr_handle))->dev;
    delta = dev->hard_header_len - skb_headroom(buf);

    if ((delta > 0) &&
            pskb_expand_head(clone, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
        kfree_skb(clone);
        return 0;
    }

    skb_reset_network_header(clone);
    clone->dev = dev;
    clone->protocol = htons(ETH_P_TIPC);
    dev_hard_header(clone, dev, ETH_P_TIPC, dest->value,
                    dev->dev_addr, clone->len);
    dev_queue_xmit(clone);
    return 0;
}