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
