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bpf: inet_diag: Dump bpf_sk_storages in inet_diag_dump()

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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: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200225230427.1976129-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau 2020-02-25 15:04:27 -08:00 committed by Alexei Starovoitov
parent 1ed4d92458
commit 085c20cacf
4 changed files with 82 additions and 2 deletions
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4
include/linux/inet_diag.h
View File

@ -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;

4
include/linux/netlink.h
View File

@ -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];

2
include/uapi/linux/inet_diag.h
View File

@ -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,
};

74
net/ipv4/inet_diag.c
View File

@ -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;