Message-ID: <MW4PR11MB5776AA2256C00293FAC07C16FD3B9@MW4PR11MB5776.namprd11.prod.outlook.com>
Date:   Tue, 22 Feb 2022 09:38:08 +0000
From:   "Drewek, Wojciech" <wojciech.drewek@...el.com>
To:     Harald Welte <laforge@...monks.org>,
        Marcin Szycik <marcin.szycik@...ux.intel.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "michal.swiatkowski@...ux.intel.com" 
        <michal.swiatkowski@...ux.intel.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pablo@...filter.org" <pablo@...filter.org>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "osmocom-net-gprs@...ts.osmocom.org" 
        <osmocom-net-gprs@...ts.osmocom.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
Subject: RE: [PATCH net-next v7 3/7] gtp: Implement GTP echo request

Hi Harald

Thanks for the response.

> -----Original Message-----
> From: Harald Welte <laforge@...monks.org>
> Sent: wtorek, 22 lutego 2022 07:33
> To: Marcin Szycik <marcin.szycik@...ux.intel.com>
> Cc: netdev@...r.kernel.org; michal.swiatkowski@...ux.intel.com; Drewek, Wojciech <wojciech.drewek@...el.com>;
> davem@...emloft.net; kuba@...nel.org; pablo@...filter.org; jiri@...nulli.us; osmocom-net-gprs@...ts.osmocom.org; intel-wired-
> lan@...ts.osuosl.org
> Subject: Re: [PATCH net-next v7 3/7] gtp: Implement GTP echo request
> 
> Hi Marcin, Wojciech,
> 
> thanks for adding this feature.
> 
> On Mon, Feb 21, 2022 at 11:14:21AM +0100, Marcin Szycik wrote:
> > All echo requests are stored in echo_hash table with the flag
> > (replied) which indicates if GTP echo response was recived in
> > response to this request. Userspace can see all echo requests
> > using GTP_CMD_ECHOREQ dumpit callback.
> 
> Is there any reason to complicate the kernel with this?  Echo requests
> are sent rately (certainly not more frequent than some seconds of timeout)
> and userspace needs to keep track of which peers there are and their state
> anyway.  So I would have expected it to handle also the receiving of
> the echo request.
> 
> I wouldn't have added the related state table.  From what I  can tell,
> there is no benefit for the kernel to have this information itself, i.e.
> there are no in-kernel users of this information?

That's right, there are no in-kernel users of this information.

> 
> It's not super critical, I just thought we should unburden the kernel
> with anything not performance critical and that it doesn't have to do
> by itself.
> 
> Also, from an "orthogonality" point of view, it is a bit unusual that
> userspace explicitly requests sending of an ECHO_REQ but then doesn't
> process the response?
> 
> I think either the Tx and the Rx ard triggered by / notified to userspace,
> or you would also do periodic triggering of Tx in the kernel autonomously,
> and process the responses.  But at that point then you also need to think
> about further consequences, such as counting the number of missed ECHO RESP,
> and then notify userspace if that condition "N out of M last responses missed".
> 
> Regards,
> 	Harald

I thought that with the GTP device created from ip link, userspace
would be unable to receive Echo Response (similar to Echo Request).
If it's not the case than I will get rid of handling Echo Response in the
next version.

Thanks,
Wojtek
> 
> >
> > Signed-off-by: Wojciech Drewek <wojciech.drewek@...el.com>
> > Suggested-by: Harald Welte <laforge@...monks.org>
> > ---
> >  drivers/net/gtp.c        | 402 ++++++++++++++++++++++++++++++++++++---
> >  include/uapi/linux/gtp.h |   2 +
> >  2 files changed, 376 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
> > index 5ed24fa9d5b2..14e9f8053d71 100644
> > --- a/drivers/net/gtp.c
> > +++ b/drivers/net/gtp.c
> > @@ -60,6 +60,19 @@ struct pdp_ctx {
> >  	struct rcu_head		rcu_head;
> >  };
> >
> > +struct gtp_echo {
> > +	struct hlist_node	hlist;
> > +
> > +	struct in_addr		ms_addr_ip4;
> > +	struct in_addr		peer_addr_ip4;
> > +
> > +	u8			replied;
> > +	u8			version;
> > +	int			ifindex;
> > +
> > +	struct rcu_head		rcu_head;
> > +};
> > +
> >  /* One instance of the GTP device. */
> >  struct gtp_dev {
> >  	struct list_head	list;
> > @@ -75,6 +88,7 @@ struct gtp_dev {
> >  	unsigned int		hash_size;
> >  	struct hlist_head	*tid_hash;
> >  	struct hlist_head	*addr_hash;
> > +	struct hlist_head	*echo_hash;
> >
> >  	u8			restart_count;
> >  };
> > @@ -89,6 +103,19 @@ static u32 gtp_h_initval;
> >
> >  static void pdp_context_delete(struct pdp_ctx *pctx);
> >
> > +static void gtp_echo_context_free(struct rcu_head *head)
> > +{
> > +	struct gtp_echo *echo = container_of(head, struct gtp_echo, rcu_head);
> > +
> > +	kfree(echo);
> > +}
> > +
> > +static void gtp_echo_delete(struct gtp_echo *echo)
> > +{
> > +	hlist_del_rcu(&echo->hlist);
> > +	call_rcu(&echo->rcu_head, gtp_echo_context_free);
> > +}
> > +
> >  static inline u32 gtp0_hashfn(u64 tid)
> >  {
> >  	u32 *tid32 = (u32 *) &tid;
> > @@ -154,6 +181,24 @@ static struct pdp_ctx *ipv4_pdp_find(struct gtp_dev *gtp, __be32 ms_addr)
> >  	return NULL;
> >  }
> >
> > +static struct gtp_echo *gtp_find_echo(struct gtp_dev *gtp, __be32 ms_addr,
> > +				      __be32 peer_addr, unsigned int version)
> > +{
> > +	struct hlist_head *head;
> > +	struct gtp_echo *echo;
> > +
> > +	head = &gtp->echo_hash[ipv4_hashfn(ms_addr) % gtp->hash_size];
> > +
> > +	hlist_for_each_entry_rcu(echo, head, hlist) {
> > +		if (echo->ms_addr_ip4.s_addr == ms_addr &&
> > +		    echo->peer_addr_ip4.s_addr == peer_addr &&
> > +		    echo->version == version)
> > +			return echo;
> > +	}
> > +
> > +	return NULL;
> > +}
> > +
> >  static bool gtp_check_ms_ipv4(struct sk_buff *skb, struct pdp_ctx *pctx,
> >  				  unsigned int hdrlen, unsigned int role)
> >  {
> > @@ -243,12 +288,34 @@ static struct rtable *ip4_route_output_gtp(struct flowi4 *fl4,
> >   *   by the receiver
> >   * Returns true if the echo req was correct, false otherwise.
> >   */
> > -static bool gtp0_validate_echo_req(struct gtp0_header *gtp0)
> > +static bool gtp0_validate_echo_hdr(struct gtp0_header *gtp0)
> >  {
> >  	return !(gtp0->tid || (gtp0->flags ^ 0x1e) ||
> >  		gtp0->number != 0xff || gtp0->flow);
> >  }
> >
> > +/* msg_type has to be GTP_ECHO_REQ or GTP_ECHO_RSP */
> > +static void gtp0_build_echo_msg(struct gtp0_header *hdr, __u8 msg_type)
> > +{
> > +	hdr->flags = 0x1e; /* v0, GTP-non-prime. */
> > +	hdr->type = msg_type;
> > +	/* GSM TS 09.60. 7.3 In all Path Management Flow Label and TID
> > +	 * are not used and shall be set to 0.
> > +	 */
> > +	hdr->flow = 0;
> > +	hdr->tid = 0;
> > +	hdr->number = 0xff;
> > +	hdr->spare[0] = 0xff;
> > +	hdr->spare[1] = 0xff;
> > +	hdr->spare[2] = 0xff;
> > +
> > +	if (msg_type == GTP_ECHO_RSP)
> > +		hdr->length =
> > +			htons(sizeof(struct gtp0_packet) - sizeof(struct gtp0_header));
> > +	else
> > +		hdr->length = 0;
> > +}
> > +
> >  static int gtp0_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >  {
> >  	struct gtp0_packet *gtp_pkt;
> > @@ -260,7 +327,7 @@ static int gtp0_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >
> >  	gtp0 = (struct gtp0_header *)(skb->data + sizeof(struct udphdr));
> >
> > -	if (!gtp0_validate_echo_req(gtp0))
> > +	if (!gtp0_validate_echo_hdr(gtp0))
> >  		return -1;
> >
> >  	seq = gtp0->seq;
> > @@ -271,10 +338,7 @@ static int gtp0_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	gtp_pkt = skb_push(skb, sizeof(struct gtp0_packet));
> >  	memset(gtp_pkt, 0, sizeof(struct gtp0_packet));
> >
> > -	gtp_pkt->gtp0_h.flags = 0x1e; /* v0, GTP-non-prime. */
> > -	gtp_pkt->gtp0_h.type = GTP_ECHO_RSP;
> > -	gtp_pkt->gtp0_h.length =
> > -		htons(sizeof(struct gtp0_packet) - sizeof(struct gtp0_header));
> > +	gtp0_build_echo_msg(&gtp_pkt->gtp0_h, GTP_ECHO_RSP);
> >
> >  	/* GSM TS 09.60. 7.3 The Sequence Number in a signalling response
> >  	 * message shall be copied from the signalling request message
> > @@ -282,16 +346,6 @@ static int gtp0_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	 */
> >  	gtp_pkt->gtp0_h.seq = seq;
> >
> > -	/* GSM TS 09.60. 7.3 In all Path Management Flow Label and TID
> > -	 * are not used and shall be set to 0.
> > -	 */
> > -	gtp_pkt->gtp0_h.flow = 0;
> > -	gtp_pkt->gtp0_h.tid = 0;
> > -	gtp_pkt->gtp0_h.number = 0xff;
> > -	gtp_pkt->gtp0_h.spare[0] = 0xff;
> > -	gtp_pkt->gtp0_h.spare[1] = 0xff;
> > -	gtp_pkt->gtp0_h.spare[2] = 0xff;
> > -
> >  	gtp_pkt->ie.tag = GTPIE_RECOVERY;
> >  	gtp_pkt->ie.val = gtp->restart_count;
> >
> > @@ -319,6 +373,31 @@ static int gtp0_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	return 0;
> >  }
> >
> > +static int gtp0_handle_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> > +{
> > +	struct gtp0_header *gtp0;
> > +	struct gtp_echo *echo;
> > +	struct iphdr *iph;
> > +
> > +	gtp0 = (struct gtp0_header *)(skb->data + sizeof(struct udphdr));
> > +
> > +	if (!gtp0_validate_echo_hdr(gtp0))
> > +		return -1;
> > +
> > +	iph = ip_hdr(skb);
> > +
> > +	echo = gtp_find_echo(gtp, iph->daddr, iph->saddr, GTP_V0);
> > +	if (!echo) {
> > +		netdev_dbg(gtp->dev, "No echo request was send to %pI4, version: %u\n",
> > +			   &iph->saddr, GTP_V0);
> > +		return -1;
> > +	}
> > +
> > +	echo->replied = true;
> > +
> > +	return 0;
> > +}
> > +
> >  /* 1 means pass up to the stack, -1 means drop and 0 means decapsulated. */
> >  static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb)
> >  {
> > @@ -342,6 +421,9 @@ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	if (gtp0->type == GTP_ECHO_REQ && gtp->sk_created)
> >  		return gtp0_send_echo_resp(gtp, skb);
> >
> > +	if (gtp0->type == GTP_ECHO_RSP && gtp->sk_created)
> > +		return gtp0_handle_echo_resp(gtp, skb);
> > +
> >  	if (gtp0->type != GTP_TPDU)
> >  		return 1;
> >
> > @@ -354,6 +436,27 @@ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	return gtp_rx(pctx, skb, hdrlen, gtp->role);
> >  }
> >
> > +/* msg_type has to be GTP_ECHO_REQ or GTP_ECHO_RSP */
> > +static void gtp1u_build_echo_msg(struct gtp1_header_long *hdr, __u8 msg_type)
> > +{
> > +	/* S flag must be set to 1 */
> > +	hdr->flags = 0x32; /* v1, GTP-non-prime. */
> > +	hdr->type = msg_type;
> > +	/* 3GPP TS 29.281 5.1 - TEID has to be set to 0 */
> > +	hdr->tid = 0;
> > +
> > +	/* seq, npdu and next should be counted to the length of the GTP packet
> > +	 * that's why szie of gtp1_header should be subtracted,
> > +	 * not size of gtp1_header_long.
> > +	 */
> > +	if (msg_type == GTP_ECHO_RSP)
> > +		hdr->length =
> > +			htons(sizeof(struct gtp1u_packet) - sizeof(struct gtp1_header));
> > +	else
> > +		hdr->length =
> > +			htons(sizeof(struct gtp1_header_long) - sizeof(struct gtp1_header));
> > +}
> > +
> >  static int gtp1u_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >  {
> >  	struct gtp1_header_long *gtp1u;
> > @@ -377,17 +480,7 @@ static int gtp1u_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	gtp_pkt = skb_push(skb, sizeof(struct gtp1u_packet));
> >  	memset(gtp_pkt, 0, sizeof(struct gtp1u_packet));
> >
> > -	/* S flag must be set to 1 */
> > -	gtp_pkt->gtp1u_h.flags = 0x32;
> > -	gtp_pkt->gtp1u_h.type = GTP_ECHO_RSP;
> > -	/* seq, npdu and next should be counted to the length of the GTP packet
> > -	 * that's why szie of gtp1_header should be subtracted,
> > -	 * not why szie of gtp1_header_long.
> > -	 */
> > -	gtp_pkt->gtp1u_h.length =
> > -		htons(sizeof(struct gtp1u_packet) - sizeof(struct gtp1_header));
> > -	/* 3GPP TS 29.281 5.1 - TEID has to be set to 0 */
> > -	gtp_pkt->gtp1u_h.tid = 0;
> > +	gtp1u_build_echo_msg(&gtp_pkt->gtp1u_h, GTP_ECHO_RSP);
> >
> >  	/* 3GPP TS 29.281 7.7.2 - The Restart Counter value in the
> >  	 * Recovery information element shall not be used, i.e. it shall
> > @@ -422,6 +515,35 @@ static int gtp1u_send_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	return 0;
> >  }
> >
> > +static int gtp1u_handle_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb)
> > +{
> > +	struct gtp1_header_long *gtp1u;
> > +	struct gtp_echo *echo;
> > +	struct iphdr *iph;
> > +
> > +	gtp1u = (struct gtp1_header_long *)(skb->data + sizeof(struct udphdr));
> > +
> > +	/* 3GPP TS 29.281 5.1 - For the Echo Request, Echo Response,
> > +	 * Error Indication and Supported Extension Headers Notification
> > +	 * messages, the S flag shall be set to 1 and TEID shall be set to 0.
> > +	 */
> > +	if (!(gtp1u->flags & GTP1_F_SEQ) || gtp1u->tid)
> > +		return -1;
> > +
> > +	iph = ip_hdr(skb);
> > +
> > +	echo = gtp_find_echo(gtp, iph->daddr, iph->saddr, GTP_V1);
> > +	if (!echo) {
> > +		netdev_dbg(gtp->dev, "No echo request was send to %pI4, version: %u\n",
> > +			   &iph->saddr, GTP_V1);
> > +		return -1;
> > +	}
> > +
> > +	echo->replied = true;
> > +
> > +	return 0;
> > +}
> > +
> >  static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb)
> >  {
> >  	unsigned int hdrlen = sizeof(struct udphdr) +
> > @@ -444,6 +566,9 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb)
> >  	if (gtp1->type == GTP_ECHO_REQ && gtp->sk_created)
> >  		return gtp1u_send_echo_resp(gtp, skb);
> >
> > +	if (gtp1->type == GTP_ECHO_RSP && gtp->sk_created)
> > +		return gtp1u_handle_echo_resp(gtp, skb);
> > +
> >  	if (gtp1->type != GTP_TPDU)
> >  		return 1;
> >
> > @@ -835,6 +960,7 @@ static void gtp_destructor(struct net_device *dev)
> >
> >  	kfree(gtp->addr_hash);
> >  	kfree(gtp->tid_hash);
> > +	kfree(gtp->echo_hash);
> >  }
> >
> >  static struct sock *gtp_create_sock(int type, struct gtp_dev *gtp)
> > @@ -954,18 +1080,23 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev,
> >  out_hashtable:
> >  	kfree(gtp->addr_hash);
> >  	kfree(gtp->tid_hash);
> > +	kfree(gtp->echo_hash);
> >  	return err;
> >  }
> >
> >  static void gtp_dellink(struct net_device *dev, struct list_head *head)
> >  {
> >  	struct gtp_dev *gtp = netdev_priv(dev);
> > +	struct gtp_echo *echo;
> >  	struct pdp_ctx *pctx;
> >  	int i;
> >
> > -	for (i = 0; i < gtp->hash_size; i++)
> > +	for (i = 0; i < gtp->hash_size; i++) {
> >  		hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid)
> >  			pdp_context_delete(pctx);
> > +		hlist_for_each_entry_rcu(echo, &gtp->echo_hash[i], hlist)
> > +			gtp_echo_delete(echo);
> > +	}
> >
> >  	list_del_rcu(&gtp->list);
> >  	unregister_netdevice_queue(dev, head);
> > @@ -1040,13 +1171,21 @@ static int gtp_hashtable_new(struct gtp_dev *gtp, int hsize)
> >  	if (gtp->tid_hash == NULL)
> >  		goto err1;
> >
> > +	gtp->echo_hash = kmalloc_array(hsize, sizeof(struct hlist_head),
> > +				       GFP_KERNEL | __GFP_NOWARN);
> > +	if (!gtp->echo_hash)
> > +		goto err2;
> > +
> >  	gtp->hash_size = hsize;
> >
> >  	for (i = 0; i < hsize; i++) {
> >  		INIT_HLIST_HEAD(&gtp->addr_hash[i]);
> >  		INIT_HLIST_HEAD(&gtp->tid_hash[i]);
> > +		INIT_HLIST_HEAD(&gtp->echo_hash[i]);
> >  	}
> >  	return 0;
> > +err2:
> > +	kfree(gtp->tid_hash);
> >  err1:
> >  	kfree(gtp->addr_hash);
> >  	return -ENOMEM;
> > @@ -1583,6 +1722,205 @@ static int gtp_genl_dump_pdp(struct sk_buff *skb,
> >  	return skb->len;
> >  }
> >
> > +static int gtp_add_echo(struct gtp_dev *gtp, __be32 src_ip, __be32 dst_ip,
> > +			unsigned int version)
> > +{
> > +	struct gtp_echo *echo;
> > +	bool found = false;
> > +
> > +	rcu_read_lock();
> > +	echo = gtp_find_echo(gtp, src_ip, dst_ip, version);
> > +	rcu_read_unlock();
> > +
> > +	if (!echo) {
> > +		echo = kmalloc(sizeof(*echo), GFP_ATOMIC);
> > +		if (!echo)
> > +			return -ENOMEM;
> > +	} else {
> > +		found = true;
> > +	}
> > +
> > +	echo->ms_addr_ip4.s_addr = src_ip;
> > +	echo->peer_addr_ip4.s_addr = dst_ip;
> > +	echo->replied = false;
> > +	echo->version = version;
> > +	echo->ifindex = gtp->dev->ifindex;
> > +
> > +	if (!found) {
> > +		u32 hash_ms;
> > +
> > +		hash_ms = ipv4_hashfn(src_ip) % gtp->hash_size;
> > +		hlist_add_head_rcu(&echo->hlist, &gtp->echo_hash[hash_ms]);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int gtp_genl_send_echo_req(struct sk_buff *skb, struct genl_info *info)
> > +{
> > +	struct sk_buff *skb_to_send;
> > +	__be32 src_ip, dst_ip;
> > +	unsigned int version;
> > +	struct gtp_dev *gtp;
> > +	struct flowi4 fl4;
> > +	struct rtable *rt;
> > +	struct sock *sk;
> > +	__be16 port;
> > +	int len;
> > +	int err;
> > +
> > +	if (!info->attrs[GTPA_VERSION] ||
> > +	    !info->attrs[GTPA_LINK] ||
> > +	    !info->attrs[GTPA_PEER_ADDRESS] ||
> > +	    !info->attrs[GTPA_MS_ADDRESS])
> > +		return -EINVAL;
> > +
> > +	version = nla_get_u32(info->attrs[GTPA_VERSION]);
> > +	dst_ip = nla_get_be32(info->attrs[GTPA_PEER_ADDRESS]);
> > +	src_ip = nla_get_be32(info->attrs[GTPA_MS_ADDRESS]);
> > +
> > +	gtp = gtp_find_dev(sock_net(skb->sk), info->attrs);
> > +	if (!gtp)
> > +		return -ENODEV;
> > +
> > +	if (!gtp->sk_created)
> > +		return -EOPNOTSUPP;
> > +	if (!(gtp->dev->flags & IFF_UP))
> > +		return -ENETDOWN;
> > +
> > +	if (version == GTP_V0) {
> > +		struct gtp0_header *gtp0_h;
> > +
> > +		len = LL_RESERVED_SPACE(gtp->dev) + sizeof(struct gtp0_header) +
> > +			sizeof(struct iphdr) + sizeof(struct udphdr);
> > +
> > +		skb_to_send = netdev_alloc_skb_ip_align(gtp->dev, len);
> > +		if (!skb_to_send)
> > +			return -ENOMEM;
> > +
> > +		sk = gtp->sk0;
> > +		port = htons(GTP0_PORT);
> > +
> > +		gtp0_h = skb_push(skb_to_send, sizeof(struct gtp0_header));
> > +		memset(gtp0_h, 0, sizeof(struct gtp0_header));
> > +		gtp0_build_echo_msg(gtp0_h, GTP_ECHO_REQ);
> > +	} else if (version == GTP_V1) {
> > +		struct gtp1_header_long *gtp1u_h;
> > +
> > +		len = LL_RESERVED_SPACE(gtp->dev) + sizeof(struct gtp1_header_long) +
> > +			sizeof(struct iphdr) + sizeof(struct udphdr);
> > +
> > +		skb_to_send = netdev_alloc_skb_ip_align(gtp->dev, len);
> > +		if (!skb_to_send)
> > +			return -ENOMEM;
> > +
> > +		sk = gtp->sk1u;
> > +		port = htons(GTP1U_PORT);
> > +
> > +		gtp1u_h = skb_push(skb_to_send, sizeof(struct gtp1_header_long));
> > +		memset(gtp1u_h, 0, sizeof(struct gtp1_header_long));
> > +		gtp1u_build_echo_msg(gtp1u_h, GTP_ECHO_REQ);
> > +	} else {
> > +		return -ENODEV;
> > +	}
> > +
> > +	rt = ip4_route_output_gtp(&fl4, sk, dst_ip, src_ip);
> > +	if (IS_ERR(rt)) {
> > +		netdev_dbg(gtp->dev, "no route for echo request to %pI4\n",
> > +			   &dst_ip);
> > +			   kfree_skb(skb_to_send);
> > +		return -ENODEV;
> > +	}
> > +
> > +	err = gtp_add_echo(gtp, src_ip, dst_ip, version);
> > +	if (err)
> > +		return err;
> > +
> > +	udp_tunnel_xmit_skb(rt, sk, skb_to_send,
> > +			    fl4.saddr, fl4.daddr,
> > +			    fl4.flowi4_tos,
> > +			    ip4_dst_hoplimit(&rt->dst),
> > +			    0,
> > +			    port, port,
> > +			    !net_eq(sock_net(sk),
> > +				    dev_net(gtp->dev)),
> > +			    false);
> > +	return 0;
> > +}
> > +
> > +static int gtp_genl_fill_echo_info(struct sk_buff *skb, u32 snd_portid, u32 snd_seq,
> > +				   int flags, u32 type, struct gtp_echo *echo)
> > +{
> > +	void *genlh;
> > +
> > +	genlh = genlmsg_put(skb, snd_portid, snd_seq, &gtp_genl_family, flags,
> > +			    type);
> > +	if (!genlh)
> > +		goto err;
> > +
> > +	if (nla_put_u32(skb, GTPA_VERSION, echo->version) ||
> > +	    nla_put_u32(skb, GTPA_LINK, echo->ifindex) ||
> > +	    nla_put_be32(skb, GTPA_PEER_ADDRESS, echo->peer_addr_ip4.s_addr) ||
> > +	    nla_put_be32(skb, GTPA_MS_ADDRESS, echo->ms_addr_ip4.s_addr) ||
> > +	    nla_put_u8(skb, GTPA_ECHO_REPLIED, echo->replied))
> > +		goto err;
> > +
> > +	genlmsg_end(skb, genlh);
> > +	return 0;
> > +
> > +err:
> > +	genlmsg_cancel(skb, genlh);
> > +	return -EMSGSIZE;
> > +}
> > +
> > +static int gtp_genl_dump_echo(struct sk_buff *skb,
> > +			      struct netlink_callback *cb)
> > +{
> > +	struct gtp_dev *last_gtp = (struct gtp_dev *)cb->args[2], *gtp;
> > +	int i, j, bucket = cb->args[0], skip = cb->args[1];
> > +	struct net *net = sock_net(skb->sk);
> > +	struct gtp_echo *echo;
> > +	struct gtp_net *gn;
> > +
> > +	gn = net_generic(net, gtp_net_id);
> > +
> > +	if (cb->args[4])
> > +		return 0;
> > +
> > +	rcu_read_lock();
> > +	list_for_each_entry_rcu(gtp, &gn->gtp_dev_list, list) {
> > +		if (last_gtp && last_gtp != gtp)
> > +			continue;
> > +		else
> > +			last_gtp = NULL;
> > +
> > +		for (i = bucket; i < gtp->hash_size; i++) {
> > +			j = 0;
> > +			hlist_for_each_entry_rcu(echo, &gtp->echo_hash[i],
> > +						 hlist) {
> > +				int ret = gtp_genl_fill_echo_info(skb,
> > +								  NETLINK_CB(cb->skb).portid,
> > +								  cb->nlh->nlmsg_seq,
> > +								  NLM_F_MULTI,
> > +								  cb->nlh->nlmsg_type, echo);
> > +				if (j >= skip && ret) {
> > +					cb->args[0] = i;
> > +					cb->args[1] = j;
> > +					cb->args[2] = (unsigned long)gtp;
> > +					goto out;
> > +				}
> > +				j++;
> > +			}
> > +			skip = 0;
> > +		}
> > +		bucket = 0;
> > +	}
> > +	cb->args[4] = 1;
> > +out:
> > +	rcu_read_unlock();
> > +	return skb->len;
> > +}
> > +
> >  static const struct nla_policy gtp_genl_policy[GTPA_MAX + 1] = {
> >  	[GTPA_LINK]		= { .type = NLA_U32, },
> >  	[GTPA_VERSION]		= { .type = NLA_U32, },
> > @@ -1593,6 +1931,7 @@ static const struct nla_policy gtp_genl_policy[GTPA_MAX + 1] = {
> >  	[GTPA_NET_NS_FD]	= { .type = NLA_U32, },
> >  	[GTPA_I_TEI]		= { .type = NLA_U32, },
> >  	[GTPA_O_TEI]		= { .type = NLA_U32, },
> > +	[GTPA_ECHO_REPLIED]	= { .type = NLA_U8, },
> >  };
> >
> >  static const struct genl_small_ops gtp_genl_ops[] = {
> > @@ -1615,6 +1954,13 @@ static const struct genl_small_ops gtp_genl_ops[] = {
> >  		.dumpit = gtp_genl_dump_pdp,
> >  		.flags = GENL_ADMIN_PERM,
> >  	},
> > +	{
> > +		.cmd = GTP_CMD_ECHOREQ,
> > +		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
> > +		.doit = gtp_genl_send_echo_req,
> > +		.dumpit = gtp_genl_dump_echo,
> > +		.flags = GENL_ADMIN_PERM,
> > +	},
> >  };
> >
> >  static struct genl_family gtp_genl_family __ro_after_init = {
> > diff --git a/include/uapi/linux/gtp.h b/include/uapi/linux/gtp.h
> > index 79f9191bbb24..63bb60f1e4e3 100644
> > --- a/include/uapi/linux/gtp.h
> > +++ b/include/uapi/linux/gtp.h
> > @@ -8,6 +8,7 @@ enum gtp_genl_cmds {
> >  	GTP_CMD_NEWPDP,
> >  	GTP_CMD_DELPDP,
> >  	GTP_CMD_GETPDP,
> > +	GTP_CMD_ECHOREQ,
> >
> >  	GTP_CMD_MAX,
> >  };
> > @@ -29,6 +30,7 @@ enum gtp_attrs {
> >  	GTPA_NET_NS_FD,
> >  	GTPA_I_TEI,	/* for GTPv1 only */
> >  	GTPA_O_TEI,	/* for GTPv1 only */
> > +	GTPA_ECHO_REPLIED,
> >  	GTPA_PAD,
> >  	__GTPA_MAX,
> >  };
> > --
> > 2.35.1
> >
> 
> --
> - Harald Welte <laforge@...monks.org>           http://laforge.gnumonks.org/
> ============================================================================
> "Privacy in residential applications is a desirable marketing option."
>                                                   (ETSI EN 300 175-7 Ch. A6)

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