Commit 085c20ca authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

bpf: inet_diag: Dump bpf_sk_storages in inet_diag_dump() 



This patch will dump out the bpf_sk_storages of a sk
if the request has the INET_DIAG_REQ_SK_BPF_STORAGES nlattr.

An array of SK_DIAG_BPF_STORAGE_REQ_MAP_FD can be specified in
INET_DIAG_REQ_SK_BPF_STORAGES to select which bpf_sk_storage to dump.
If no map_fd is specified, all bpf_sk_storages of a sk will be dumped.

bpf_sk_storages can be added to the system at runtime.  It is difficult
to find a proper static value for cb->min_dump_alloc.

This patch learns the nlattr size required to dump the bpf_sk_storages
of a sk.  If it happens to be the very first nlmsg of a dump and it
cannot fit the needed bpf_sk_storages,  it will try to expand the
skb by "pskb_expand_head()".

Instead of expanding it in inet_sk_diag_fill(), it is expanded at a
sleepable context in __inet_diag_dump() so __GFP_DIRECT_RECLAIM can
be used.  In __inet_diag_dump(), it will retry as long as the
skb is empty and the cb->min_dump_alloc becomes larger than before.
cb->min_dump_alloc is bounded by KMALLOC_MAX_SIZE.  The min_dump_alloc
is also changed from 'u16' to 'u32' to accommodate a sk that may have
a few large bpf_sk_storages.

The updated cb->min_dump_alloc will also be used to allocate the skb in
the next dump.  This logic already exists in netlink_dump().

Here is the sample output of a locally modified 'ss' and it could be made
more readable by using BTF later:
[root@arch-fb-vm1 ~]# ss --bpf-map-id 14 --bpf-map-id 13 -t6an 'dst [::1]:8989'
State Recv-Q Send-Q Local Address:Port  Peer Address:PortProcess
ESTAB 0      0              [::1]:51072        [::1]:8989
	 bpf_map_id:14 value:[ 3feb ]
	 bpf_map_id:13 value:[ 3f ]
ESTAB 0      0              [::1]:51070        [::1]:8989
	 bpf_map_id:14 value:[ 3feb ]
	 bpf_map_id:13 value:[ 3f ]

[root@arch-fb-vm1 ~]# ~/devshare/github/iproute2/misc/ss --bpf-maps -t6an 'dst [::1]:8989'
State         Recv-Q         Send-Q                   Local Address:Port                    Peer Address:Port         Process
ESTAB         0              0                                [::1]:51072                          [::1]:8989
	 bpf_map_id:14 value:[ 3feb ]
	 bpf_map_id:13 value:[ 3f ]
	 bpf_map_id:12 value:[ 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000... total:65407 ]
ESTAB         0              0                                [::1]:51070                          [::1]:8989
	 bpf_map_id:14 value:[ 3feb ]
	 bpf_map_id:13 value:[ 3f ]
	 bpf_map_id:12 value:[ 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000... total:65407 ]

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200225230427.1976129-1-kafai@fb.com
parent 1ed4d924

include/linux/inet_diag.h

+4 −0
Original line number Diff line number Diff line
@@ -38,9 +38,13 @@ struct inet_diag_handler { 
	__u16		idiag_info_size;

};



struct bpf_sk_storage_diag;

struct inet_diag_dump_data {

	struct nlattr *req_nlas[__INET_DIAG_REQ_MAX];

#define inet_diag_nla_bc req_nlas[INET_DIAG_REQ_BYTECODE]

#define inet_diag_nla_bpf_stgs req_nlas[INET_DIAG_REQ_SK_BPF_STORAGES]



	struct bpf_sk_storage_diag *bpf_stg_diag;

};



struct inet_connection_sock;

include/linux/netlink.h

+2 −2
Original line number Diff line number Diff line
@@ -188,10 +188,10 @@ struct netlink_callback { 
	struct module		*module;

	struct netlink_ext_ack	*extack;

	u16			family;

	u16			min_dump_alloc;

	bool			strict_check;

	u16			answer_flags;

	u32			min_dump_alloc;

	unsigned int		prev_seq, seq;

	bool			strict_check;

	union {

		u8		ctx[48];

include/uapi/linux/inet_diag.h

+2 −0
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ struct inet_diag_req_raw { 
enum {

	INET_DIAG_REQ_NONE,

	INET_DIAG_REQ_BYTECODE,

	INET_DIAG_REQ_SK_BPF_STORAGES,

	__INET_DIAG_REQ_MAX,

};
@@ -155,6 +156,7 @@ enum { 
	INET_DIAG_CLASS_ID,	/* request as INET_DIAG_TCLASS */

	INET_DIAG_MD5SIG,

	INET_DIAG_ULP_INFO,

	INET_DIAG_SK_BPF_STORAGES,

	__INET_DIAG_MAX,

};

net/ipv4/inet_diag.c

+74 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <net/inet_hashtables.h>

#include <net/inet_timewait_sock.h>

#include <net/inet6_hashtables.h>

#include <net/bpf_sk_storage.h>

#include <net/netlink.h>



#include <linux/inet.h>
@@ -156,6 +157,8 @@ errout: 
}

EXPORT_SYMBOL_GPL(inet_diag_msg_attrs_fill);



#define MAX_DUMP_ALLOC_SIZE (KMALLOC_MAX_SIZE - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))



int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,

		      struct sk_buff *skb, struct netlink_callback *cb,

		      const struct inet_diag_req_v2 *req,
@@ -163,12 +166,14 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk, 
{

	const struct tcp_congestion_ops *ca_ops;

	const struct inet_diag_handler *handler;

	struct inet_diag_dump_data *cb_data;

	int ext = req->idiag_ext;

	struct inet_diag_msg *r;

	struct nlmsghdr  *nlh;

	struct nlattr *attr;

	void *info = NULL;



	cb_data = cb->data;

	handler = inet_diag_table[req->sdiag_protocol];

	BUG_ON(!handler);
@@ -302,6 +307,48 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk, 
			goto errout;

	}



	/* Keep it at the end for potential retry with a larger skb,

	 * or else do best-effort fitting, which is only done for the

	 * first_nlmsg.

	 */

	if (cb_data->bpf_stg_diag) {

		bool first_nlmsg = ((unsigned char *)nlh == skb->data);

		unsigned int prev_min_dump_alloc;

		unsigned int total_nla_size = 0;

		unsigned int msg_len;

		int err;



		msg_len = skb_tail_pointer(skb) - (unsigned char *)nlh;

		err = bpf_sk_storage_diag_put(cb_data->bpf_stg_diag, sk, skb,

					      INET_DIAG_SK_BPF_STORAGES,

					      &total_nla_size);



		if (!err)

			goto out;



		total_nla_size += msg_len;

		prev_min_dump_alloc = cb->min_dump_alloc;

		if (total_nla_size > prev_min_dump_alloc)

			cb->min_dump_alloc = min_t(u32, total_nla_size,

						   MAX_DUMP_ALLOC_SIZE);



		if (!first_nlmsg)

			goto errout;



		if (cb->min_dump_alloc > prev_min_dump_alloc)

			/* Retry with pskb_expand_head() with

			 * __GFP_DIRECT_RECLAIM

			 */

			goto errout;



		WARN_ON_ONCE(total_nla_size <= prev_min_dump_alloc);



		/* Send what we have for this sk

		 * and move on to the next sk in the following

		 * dump()

		 */

	}



out:

	nlmsg_end(skb, nlh);

	return 0;
@@ -1022,8 +1069,11 @@ static int __inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, 
			    const struct inet_diag_req_v2 *r)

{

	const struct inet_diag_handler *handler;

	u32 prev_min_dump_alloc;

	int err = 0;



again:

	prev_min_dump_alloc = cb->min_dump_alloc;

	handler = inet_diag_lock_handler(r->sdiag_protocol);

	if (!IS_ERR(handler))

		handler->dump(skb, cb, r);
@@ -1031,6 +1081,15 @@ static int __inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, 
		err = PTR_ERR(handler);

	inet_diag_unlock_handler(handler);



	/* The skb is not large enough to fit one sk info and

	 * inet_sk_diag_fill() has requested for a larger skb.

	 */

	if (!skb->len && cb->min_dump_alloc > prev_min_dump_alloc) {

		err = pskb_expand_head(skb, 0, cb->min_dump_alloc, GFP_KERNEL);

		if (!err)

			goto again;

	}



	return err ? : skb->len;

}
@@ -1068,6 +1127,18 @@ static int __inet_diag_dump_start(struct netlink_callback *cb, int hdrlen) 
		}

	}



	nla = cb_data->inet_diag_nla_bpf_stgs;

	if (nla) {

		struct bpf_sk_storage_diag *bpf_stg_diag;



		bpf_stg_diag = bpf_sk_storage_diag_alloc(nla);

		if (IS_ERR(bpf_stg_diag)) {

			kfree(cb_data);

			return PTR_ERR(bpf_stg_diag);

		}

		cb_data->bpf_stg_diag = bpf_stg_diag;

	}



	cb->data = cb_data;

	return 0;

}
@@ -1084,6 +1155,9 @@ static int inet_diag_dump_start_compat(struct netlink_callback *cb) 


static int inet_diag_dump_done(struct netlink_callback *cb)

{

	struct inet_diag_dump_data *cb_data = cb->data;



	bpf_sk_storage_diag_free(cb_data->bpf_stg_diag);

	kfree(cb->data);



	return 0;

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