Subject: Re: [PATCH bpf-next] net: netfilter: move bpf_ct_set_nat_info kfunc in nf_nat_bpf.c

From: Yauheni Kaliuta <[email-masked]>
Date: Thu, 29 Sep 2022 12:27:32 +0300

Hi!

>>>>> On Thu, 29 Sep 2022 11:37:49 +0300, Yauheni Kaliuta  wrote:

 > Hi!
 > The patch leads to

 > depmod: ERROR: Cycle detected: nf_conntrack -> nf_nat -> nf_conntrack

 > when it is built as modules (due to nf_nat_setup_info() dependency)

Oops, I replied to the actual fix :)
Sorry for the noise.

 > On Sun, Sep 25, 2022 at 4:26 PM Lorenzo Bianconi <[email-masked]> wrote:
 >> 
 >> Remove circular dependency between nf_nat module and nf_conntrack one
 >> moving bpf_ct_set_nat_info kfunc in nf_nat_bpf.c
 >> 
 >> Fixes: 0fabd2aa199f ("net: netfilter: add bpf_ct_set_nat_info kfunc helper")
 >> Suggested-by: Kumar Kartikeya Dwivedi <[email-masked]>
 >> Tested-by: Nathan Chancellor <[email-masked]>
 >> Signed-off-by: Lorenzo Bianconi <[email-masked]>
 >> ---
 >> include/net/netfilter/nf_conntrack_bpf.h |  5 ++
 >> include/net/netfilter/nf_nat.h           | 14 +++++
 >> net/netfilter/Makefile                   |  6 ++
 >> net/netfilter/nf_conntrack_bpf.c         | 49 ---------------
 >> net/netfilter/nf_nat_bpf.c               | 79 ++++++++++++++++++++++++
 >> net/netfilter/nf_nat_core.c              |  2 +-
 >> 6 files changed, 105 insertions(+), 50 deletions(-)
 >> create mode 100644 net/netfilter/nf_nat_bpf.c
 >> 
 >> diff --git a/include/net/netfilter/nf_conntrack_bpf.h b/include/net/netfilter/nf_conntrack_bpf.h
 >> index c8b80add1142..1ce46e406062 100644
 >> --- a/include/net/netfilter/nf_conntrack_bpf.h
 >> +++ b/include/net/netfilter/nf_conntrack_bpf.h
 >> @@ -4,6 +4,11 @@
 >> #define _NF_CONNTRACK_BPF_H
 >> 
 >> #include <linux/kconfig.h>
 >> +#include <net/netfilter/nf_conntrack.h>
 >> +
 >> +struct nf_conn___init {
 >> +       struct nf_conn ct;
 >> +};
 >> 
 >> #if (IS_BUILTIN(CONFIG_NF_CONNTRACK) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) || \
 >> (IS_MODULE(CONFIG_NF_CONNTRACK) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
 >> diff --git a/include/net/netfilter/nf_nat.h b/include/net/netfilter/nf_nat.h
 >> index e9eb01e99d2f..cd084059a953 100644
 >> --- a/include/net/netfilter/nf_nat.h
 >> +++ b/include/net/netfilter/nf_nat.h
 >> @@ -68,6 +68,20 @@ static inline bool nf_nat_oif_changed(unsigned int hooknum,
 >> #endif
 >> }
 >> 
 >> +#if (IS_BUILTIN(CONFIG_NF_NAT) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) || \
 >> +    (IS_MODULE(CONFIG_NF_NAT) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
 >> +
 >> +extern int register_nf_nat_bpf(void);
 >> +
 >> +#else
 >> +
 >> +static inline int register_nf_nat_bpf(void)
 >> +{
 >> +       return 0;
 >> +}
 >> +
 >> +#endif
 >> +
 >> int nf_nat_register_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 >> const struct nf_hook_ops *nat_ops, unsigned int ops_count);
 >> void nf_nat_unregister_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 >> diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
 >> index 06df49ea6329..0f060d100880 100644
 >> --- a/net/netfilter/Makefile
 >> +++ b/net/netfilter/Makefile
 >> @@ -60,6 +60,12 @@ obj-$(CONFIG_NF_NAT) += nf_nat.o
 >> nf_nat-$(CONFIG_NF_NAT_REDIRECT) += nf_nat_redirect.o
 >> nf_nat-$(CONFIG_NF_NAT_MASQUERADE) += nf_nat_masquerade.o
 >> 
 >> +ifeq ($(CONFIG_NF_NAT),m)
 >> +nf_nat-$(CONFIG_DEBUG_INFO_BTF_MODULES) += nf_nat_bpf.o
 >> +else ifeq ($(CONFIG_NF_NAT),y)
 >> +nf_nat-$(CONFIG_DEBUG_INFO_BTF) += nf_nat_bpf.o
 >> +endif
 >> +
 >> # NAT helpers
 >> obj-$(CONFIG_NF_NAT_AMANDA) += nf_nat_amanda.o
 >> obj-$(CONFIG_NF_NAT_FTP) += nf_nat_ftp.o
 >> diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
 >> index 756ea818574e..f4ba4ff3a63b 100644
 >> --- a/net/netfilter/nf_conntrack_bpf.c
 >> +++ b/net/netfilter/nf_conntrack_bpf.c
 >> @@ -14,7 +14,6 @@
 >> #include <linux/types.h>
 >> #include <linux/btf_ids.h>
 >> #include <linux/net_namespace.h>
 >> -#include <net/netfilter/nf_conntrack.h>
 >> #include <net/netfilter/nf_conntrack_bpf.h>
 >> #include <net/netfilter/nf_conntrack_core.h>
 >> #include <net/netfilter/nf_nat.h>
 >> @@ -239,10 +238,6 @@ __diag_push();
 >> __diag_ignore_all("-Wmissing-prototypes",
 >> "Global functions as their definitions will be in nf_conntrack BTF");
 >> 
 >> -struct nf_conn___init {
 >> -       struct nf_conn ct;
 >> -};
 >> -
 >> /* bpf_xdp_ct_alloc - Allocate a new CT entry
 >> *
 >> * Parameters:
 >> @@ -476,49 +471,6 @@ int bpf_ct_change_status(struct nf_conn *nfct, u32 status)
 >> return nf_ct_change_status_common(nfct, status);
 >> }
 >> 
 >> -/* bpf_ct_set_nat_info - Set source or destination nat address
 >> - *
 >> - * Set source or destination nat address of the newly allocated
 >> - * nf_conn before insertion. This must be invoked for referenced
 >> - * PTR_TO_BTF_ID to nf_conn___init.
 >> - *
 >> - * Parameters:
 >> - * @nfct       - Pointer to referenced nf_conn object, obtained using
 >> - *               bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 >> - * @addr       - Nat source/destination address
 >> - * @port       - Nat source/destination port. Non-positive values are
 >> - *               interpreted as select a random port.
 >> - * @manip      - NF_NAT_MANIP_SRC or NF_NAT_MANIP_DST
 >> - */
 >> -int bpf_ct_set_nat_info(struct nf_conn___init *nfct,
 >> -                       union nf_inet_addr *addr, int port,
 >> -                       enum nf_nat_manip_type manip)
 >> -{
 >> -#if ((IS_MODULE(CONFIG_NF_NAT) && IS_MODULE(CONFIG_NF_CONNTRACK)) || \
 >> -     IS_BUILTIN(CONFIG_NF_NAT))
 >> -       struct nf_conn *ct = (struct nf_conn *)nfct;
 >> -       u16 proto = nf_ct_l3num(ct);
 >> -       struct nf_nat_range2 range;
 >> -
 >> -       if (proto != NFPROTO_IPV4 && proto != NFPROTO_IPV6)
 >> -               return -EINVAL;
 >> -
 >> -       memset(&range, 0, sizeof(struct nf_nat_range2));
 >> -       range.flags = NF_NAT_RANGE_MAP_IPS;
 >> -       range.min_addr = *addr;
 >> -       range.max_addr = range.min_addr;
 >> -       if (port > 0) {
 >> -               range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
 >> -               range.min_proto.all = cpu_to_be16(port);
 >> -               range.max_proto.all = range.min_proto.all;
 >> -       }
 >> -
 >> -       return nf_nat_setup_info(ct, &range, manip) == NF_DROP ? -ENOMEM : 0;
 >> -#else
 >> -       return -EOPNOTSUPP;
 >> -#endif
 >> -}
 >> -
 >> __diag_pop()
 >> 
 >> BTF_SET8_START(nf_ct_kfunc_set)
 >> @@ -532,7 +484,6 @@ BTF_ID_FLAGS(func, bpf_ct_set_timeout, KF_TRUSTED_ARGS)
 >> BTF_ID_FLAGS(func, bpf_ct_change_timeout, KF_TRUSTED_ARGS)
 >> BTF_ID_FLAGS(func, bpf_ct_set_status, KF_TRUSTED_ARGS)
 >> BTF_ID_FLAGS(func, bpf_ct_change_status, KF_TRUSTED_ARGS)
 >> -BTF_ID_FLAGS(func, bpf_ct_set_nat_info, KF_TRUSTED_ARGS)
 >> BTF_SET8_END(nf_ct_kfunc_set)
 >> 
 >> static const struct btf_kfunc_id_set nf_conntrack_kfunc_set = {
 >> diff --git a/net/netfilter/nf_nat_bpf.c b/net/netfilter/nf_nat_bpf.c
 >> new file mode 100644
 >> index 000000000000..0fa5a0bbb0ff
 >> --- /dev/null
 >> +++ b/net/netfilter/nf_nat_bpf.c
 >> @@ -0,0 +1,79 @@
 >> +// SPDX-License-Identifier: GPL-2.0-only
 >> +/* Unstable NAT Helpers for XDP and TC-BPF hook
 >> + *
 >> + * These are called from the XDP and SCHED_CLS BPF programs. Note that it is
 >> + * allowed to break compatibility for these functions since the interface they
 >> + * are exposed through to BPF programs is explicitly unstable.
 >> + */
 >> +
 >> +#include <linux/bpf.h>
 >> +#include <linux/btf_ids.h>
 >> +#include <net/netfilter/nf_conntrack_bpf.h>
 >> +#include <net/netfilter/nf_conntrack_core.h>
 >> +#include <net/netfilter/nf_nat.h>
 >> +
 >> +__diag_push();
 >> +__diag_ignore_all("-Wmissing-prototypes",
 >> +                 "Global functions as their definitions will be in nf_nat BTF");
 >> +
 >> +/* bpf_ct_set_nat_info - Set source or destination nat address
 >> + *
 >> + * Set source or destination nat address of the newly allocated
 >> + * nf_conn before insertion. This must be invoked for referenced
 >> + * PTR_TO_BTF_ID to nf_conn___init.
 >> + *
 >> + * Parameters:
 >> + * @nfct       - Pointer to referenced nf_conn object, obtained using
 >> + *               bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 >> + * @addr       - Nat source/destination address
 >> + * @port       - Nat source/destination port. Non-positive values are
 >> + *               interpreted as select a random port.
 >> + * @manip      - NF_NAT_MANIP_SRC or NF_NAT_MANIP_DST
 >> + */
 >> +int bpf_ct_set_nat_info(struct nf_conn___init *nfct,
 >> +                       union nf_inet_addr *addr, int port,
 >> +                       enum nf_nat_manip_type manip)
 >> +{
 >> +       struct nf_conn *ct = (struct nf_conn *)nfct;
 >> +       u16 proto = nf_ct_l3num(ct);
 >> +       struct nf_nat_range2 range;
 >> +
 >> +       if (proto != NFPROTO_IPV4 && proto != NFPROTO_IPV6)
 >> +               return -EINVAL;
 >> +
 >> +       memset(&range, 0, sizeof(struct nf_nat_range2));
 >> +       range.flags = NF_NAT_RANGE_MAP_IPS;
 >> +       range.min_addr = *addr;
 >> +       range.max_addr = range.min_addr;
 >> +       if (port > 0) {
 >> +               range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
 >> +               range.min_proto.all = cpu_to_be16(port);
 >> +               range.max_proto.all = range.min_proto.all;
 >> +       }
 >> +
 >> +       return nf_nat_setup_info(ct, &range, manip) == NF_DROP ? -ENOMEM : 0;
 >> +}
 >> +
 >> +__diag_pop()
 >> +
 >> +BTF_SET8_START(nf_nat_kfunc_set)
 >> +BTF_ID_FLAGS(func, bpf_ct_set_nat_info, KF_TRUSTED_ARGS)
 >> +BTF_SET8_END(nf_nat_kfunc_set)
 >> +
 >> +static const struct btf_kfunc_id_set nf_bpf_nat_kfunc_set = {
 >> +       .owner = THIS_MODULE,
 >> +       .set   = &nf_nat_kfunc_set,
 >> +};
 >> +
 >> +int register_nf_nat_bpf(void)
 >> +{
 >> +       int ret;
 >> +
 >> +       ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP,
 >> +                                       &nf_bpf_nat_kfunc_set);
 >> +       if (ret)
 >> +               return ret;
 >> +
 >> +       return register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS,
 >> +                                        &nf_bpf_nat_kfunc_set);
 >> +}
 >> diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
 >> index 7981be526f26..1ed09c9af5e5 100644
 >> --- a/net/netfilter/nf_nat_core.c
 >> +++ b/net/netfilter/nf_nat_core.c
 >> @@ -1152,7 +1152,7 @@ static int __init nf_nat_init(void)
 >> WARN_ON(nf_nat_hook != NULL);
 >> RCU_INIT_POINTER(nf_nat_hook, &nat_hook);
 >> 
 >> -       return 0;
 >> +       return register_nf_nat_bpf();
 >> }
 >> 
 >> static void __exit nf_nat_cleanup(void)
 >> --
 >> 2.37.3
 >> 

 > -- 
 > WBR, Yauheni

-- 
WBR,
Yauheni Kaliuta