On Mon, Feb 24, 2020 at 09:47:33PM -0800, Song Liu wrote:
> On Fri, Feb 21, 2020 at 10:49 AM Martin KaFai Lau <kafai@xxxxxx> wrote:
> >
> > 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.
> [...]
>
> > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
> > ---
> > include/linux/inet_diag.h | 4 ++
> > include/linux/netlink.h | 4 +-
> > include/uapi/linux/inet_diag.h | 2 +
> > net/ipv4/inet_diag.c | 71 ++++++++++++++++++++++++++++++++++
> > 4 files changed, 79 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/inet_diag.h b/include/linux/inet_diag.h
> > index 1bb94cac265f..e4ba25d63913 100644
> > --- a/include/linux/inet_diag.h
> > +++ b/include/linux/inet_diag.h
> > @@ -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;
> > diff --git a/include/linux/netlink.h b/include/linux/netlink.h
> > index 205fa7b1f07a..788969ccbbde 100644
> > --- a/include/linux/netlink.h
> > +++ b/include/linux/netlink.h
> > @@ -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;
>
> Maybe highlight this change in the commit log?
ok.
>
> > unsigned int prev_seq, seq;
> > + bool strict_check;
> > union {
> > u8 ctx[48];
> >
[ ... ]
> > diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
> > index 4bce8a477699..8ca4d54d7c5a 100644
[ ... ]
> > @@ -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 +1081,12 @@ static int __inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
> > err = PTR_ERR(handler);
> > inet_diag_unlock_handler(handler);
> >
> > + if (!skb->len && cb->min_dump_alloc > prev_min_dump_alloc) {
>
> Why do we check for !skb->len here?
skb contains the info of sk(s) to be dumped to the userspace.
It may contain no sk info (i.e. !skb->len), 1 sk info, 2 sk info...etc.
It only retries if there is no sk info and the cb->min_dump_alloc becomes
larger (together, it means the current skb is not large enough to fit one
sk info).
>
> > + err = pskb_expand_head(skb, 0, cb->min_dump_alloc, GFP_KERNEL);
> > + if (!err)
> > + goto again;
> > + }
> > +
> > return err ? : skb->len;
> > }
> >
