text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * net/psample/psample.c - Netlink channel for packet sampling
   * Copyright (c) 2017 Yotam Gigi <yotamg@mellanox.com>
   */
  
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/skbuff.h>
  #include <linux/module.h>
  #include <net/net_namespace.h>
  #include <net/sock.h>
  #include <net/netlink.h>
  #include <net/genetlink.h>
  #include <net/psample.h>
  #include <linux/spinlock.h>
  
  #define PSAMPLE_MAX_PACKET_SIZE 0xffff
  
  static LIST_HEAD(psample_groups_list);
  static DEFINE_SPINLOCK(psample_groups_lock);
  
  /* multicast groups */
  enum psample_nl_multicast_groups {
  	PSAMPLE_NL_MCGRP_CONFIG,
  	PSAMPLE_NL_MCGRP_SAMPLE,
  };
  
  static const struct genl_multicast_group psample_nl_mcgrps[] = {
  	[PSAMPLE_NL_MCGRP_CONFIG] = { .name = PSAMPLE_NL_MCGRP_CONFIG_NAME },
  	[PSAMPLE_NL_MCGRP_SAMPLE] = { .name = PSAMPLE_NL_MCGRP_SAMPLE_NAME },
  };
  
  static struct genl_family psample_nl_family __ro_after_init;
  
  static int psample_group_nl_fill(struct sk_buff *msg,
  				 struct psample_group *group,
  				 enum psample_command cmd, u32 portid, u32 seq,
  				 int flags)
  {
  	void *hdr;
  	int ret;
  
  	hdr = genlmsg_put(msg, portid, seq, &psample_nl_family, flags, cmd);
  	if (!hdr)
  		return -EMSGSIZE;
  
  	ret = nla_put_u32(msg, PSAMPLE_ATTR_SAMPLE_GROUP, group->group_num);
  	if (ret < 0)
  		goto error;
  
  	ret = nla_put_u32(msg, PSAMPLE_ATTR_GROUP_REFCOUNT, group->refcount);
  	if (ret < 0)
  		goto error;
  
  	ret = nla_put_u32(msg, PSAMPLE_ATTR_GROUP_SEQ, group->seq);
  	if (ret < 0)
  		goto error;
  
  	genlmsg_end(msg, hdr);
  	return 0;
  
  error:
  	genlmsg_cancel(msg, hdr);
  	return -EMSGSIZE;
  }
  
  static int psample_nl_cmd_get_group_dumpit(struct sk_buff *msg,
  					   struct netlink_callback *cb)
  {
  	struct psample_group *group;
  	int start = cb->args[0];
  	int idx = 0;
  	int err;
  
  	spin_lock(&psample_groups_lock);
  	list_for_each_entry(group, &psample_groups_list, list) {
  		if (!net_eq(group->net, sock_net(msg->sk)))
  			continue;
  		if (idx < start) {
  			idx++;
  			continue;
  		}
  		err = psample_group_nl_fill(msg, group, PSAMPLE_CMD_NEW_GROUP,
  					    NETLINK_CB(cb->skb).portid,
  					    cb->nlh->nlmsg_seq, NLM_F_MULTI);
  		if (err)
  			break;
  		idx++;
  	}
  
  	spin_unlock(&psample_groups_lock);
  	cb->args[0] = idx;
  	return msg->len;
  }
  
  static const struct genl_ops psample_nl_ops[] = {
  	{
  		.cmd = PSAMPLE_CMD_GET_GROUP,
  		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
  		.dumpit = psample_nl_cmd_get_group_dumpit,
  		/* can be retrieved by unprivileged users */
  	}
  };
  
  static struct genl_family psample_nl_family __ro_after_init = {
  	.name		= PSAMPLE_GENL_NAME,
  	.version	= PSAMPLE_GENL_VERSION,
  	.maxattr	= PSAMPLE_ATTR_MAX,
  	.netnsok	= true,
  	.module		= THIS_MODULE,
  	.mcgrps		= psample_nl_mcgrps,
  	.ops		= psample_nl_ops,
  	.n_ops		= ARRAY_SIZE(psample_nl_ops),
  	.n_mcgrps	= ARRAY_SIZE(psample_nl_mcgrps),
  };
  
  static void psample_group_notify(struct psample_group *group,
  				 enum psample_command cmd)
  {
  	struct sk_buff *msg;
  	int err;
  
  	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
  	if (!msg)
  		return;
  
  	err = psample_group_nl_fill(msg, group, cmd, 0, 0, NLM_F_MULTI);
  	if (!err)
  		genlmsg_multicast_netns(&psample_nl_family, group->net, msg, 0,
  					PSAMPLE_NL_MCGRP_CONFIG, GFP_ATOMIC);
  	else
  		nlmsg_free(msg);
  }
  
  static struct psample_group *psample_group_create(struct net *net,
  						  u32 group_num)
  {
  	struct psample_group *group;
  
  	group = kzalloc(sizeof(*group), GFP_ATOMIC);
  	if (!group)
  		return NULL;
  
  	group->net = net;
  	group->group_num = group_num;
  	list_add_tail(&group->list, &psample_groups_list);
  
  	psample_group_notify(group, PSAMPLE_CMD_NEW_GROUP);
  	return group;
  }
  
  static void psample_group_destroy(struct psample_group *group)
  {
  	psample_group_notify(group, PSAMPLE_CMD_DEL_GROUP);
  	list_del(&group->list);
  	kfree_rcu(group, rcu);
  }
  
  static struct psample_group *
  psample_group_lookup(struct net *net, u32 group_num)
  {
  	struct psample_group *group;
  
  	list_for_each_entry(group, &psample_groups_list, list)
  		if ((group->group_num == group_num) && (group->net == net))
  			return group;
  	return NULL;
  }
  
  struct psample_group *psample_group_get(struct net *net, u32 group_num)
  {
  	struct psample_group *group;
  
  	spin_lock(&psample_groups_lock);
  
  	group = psample_group_lookup(net, group_num);
  	if (!group) {
  		group = psample_group_create(net, group_num);
  		if (!group)
  			goto out;
  	}
  	group->refcount++;
  
  out:
  	spin_unlock(&psample_groups_lock);
  	return group;
  }
  EXPORT_SYMBOL_GPL(psample_group_get);
  
  void psample_group_put(struct psample_group *group)
  {
  	spin_lock(&psample_groups_lock);
  
  	if (--group->refcount == 0)
  		psample_group_destroy(group);
  
  	spin_unlock(&psample_groups_lock);
  }
  EXPORT_SYMBOL_GPL(psample_group_put);
  
  void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
  			   u32 trunc_size, int in_ifindex, int out_ifindex,
  			   u32 sample_rate)
  {
  	struct sk_buff *nl_skb;
  	int data_len;
  	int meta_len;
  	void *data;
  	int ret;
  
  	meta_len = (in_ifindex ? nla_total_size(sizeof(u16)) : 0) +
  		   (out_ifindex ? nla_total_size(sizeof(u16)) : 0) +
  		   nla_total_size(sizeof(u32)) +	/* sample_rate */
  		   nla_total_size(sizeof(u32)) +	/* orig_size */
  		   nla_total_size(sizeof(u32)) +	/* group_num */
  		   nla_total_size(sizeof(u32));		/* seq */
  
  	data_len = min(skb->len, trunc_size);
  	if (meta_len + nla_total_size(data_len) > PSAMPLE_MAX_PACKET_SIZE)
  		data_len = PSAMPLE_MAX_PACKET_SIZE - meta_len - NLA_HDRLEN
  			    - NLA_ALIGNTO;
  
  	nl_skb = genlmsg_new(meta_len + data_len, GFP_ATOMIC);
  	if (unlikely(!nl_skb))
  		return;
  
  	data = genlmsg_put(nl_skb, 0, 0, &psample_nl_family, 0,
  			   PSAMPLE_CMD_SAMPLE);
  	if (unlikely(!data))
  		goto error;
  
  	if (in_ifindex) {
  		ret = nla_put_u16(nl_skb, PSAMPLE_ATTR_IIFINDEX, in_ifindex);
  		if (unlikely(ret < 0))
  			goto error;
  	}
  
  	if (out_ifindex) {
  		ret = nla_put_u16(nl_skb, PSAMPLE_ATTR_OIFINDEX, out_ifindex);
  		if (unlikely(ret < 0))
  			goto error;
  	}
  
  	ret = nla_put_u32(nl_skb, PSAMPLE_ATTR_SAMPLE_RATE, sample_rate);
  	if (unlikely(ret < 0))
  		goto error;
  
  	ret = nla_put_u32(nl_skb, PSAMPLE_ATTR_ORIGSIZE, skb->len);
  	if (unlikely(ret < 0))
  		goto error;
  
  	ret = nla_put_u32(nl_skb, PSAMPLE_ATTR_SAMPLE_GROUP, group->group_num);
  	if (unlikely(ret < 0))
  		goto error;
  
  	ret = nla_put_u32(nl_skb, PSAMPLE_ATTR_GROUP_SEQ, group->seq++);
  	if (unlikely(ret < 0))
  		goto error;
  
  	if (data_len) {
  		int nla_len = nla_total_size(data_len);
  		struct nlattr *nla;
  
  		nla = skb_put(nl_skb, nla_len);
  		nla->nla_type = PSAMPLE_ATTR_DATA;
  		nla->nla_len = nla_attr_size(data_len);
  
  		if (skb_copy_bits(skb, 0, nla_data(nla), data_len))
  			goto error;
  	}
  
  	genlmsg_end(nl_skb, data);
  	genlmsg_multicast_netns(&psample_nl_family, group->net, nl_skb, 0,
  				PSAMPLE_NL_MCGRP_SAMPLE, GFP_ATOMIC);
  
  	return;
  error:
  	pr_err_ratelimited("Could not create psample log message\n");
  	nlmsg_free(nl_skb);
  }
  EXPORT_SYMBOL_GPL(psample_sample_packet);
  
  static int __init psample_module_init(void)
  {
  	return genl_register_family(&psample_nl_family);
  }
  
  static void __exit psample_module_exit(void)
  {
  	genl_unregister_family(&psample_nl_family);
  }
  
  module_init(psample_module_init);
  module_exit(psample_module_exit);
  
  MODULE_AUTHOR("Yotam Gigi <yotam.gi@gmail.com>");
  MODULE_DESCRIPTION("netlink channel for packet sampling");
  MODULE_LICENSE("GPL v2");
  