diff options
author | Daniel Xu <dxu@dxuuu.xyz> | 2022-09-07 19:40:40 +0300 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2022-09-11 03:27:32 +0300 |
commit | 864b656f82ccd433d3e38149c3673d295ad64bf6 (patch) | |
tree | 1c4c3a628e740c3657756f4b8bc7c440bd948c84 /net/netfilter/nf_conntrack_bpf.c | |
parent | 84c6ac417ceacd086efc330afece8922969610b7 (diff) | |
download | linux-864b656f82ccd433d3e38149c3673d295ad64bf6.tar.xz |
bpf: Add support for writing to nf_conn:mark
Support direct writes to nf_conn:mark from TC and XDP prog types. This
is useful when applications want to store per-connection metadata. This
is also particularly useful for applications that run both bpf and
iptables/nftables because the latter can trivially access this metadata.
One example use case would be if a bpf prog is responsible for advanced
packet classification and iptables/nftables is later used for routing
due to pre-existing/legacy code.
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/ebca06dea366e3e7e861c12f375a548cc4c61108.1662568410.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'net/netfilter/nf_conntrack_bpf.c')
-rw-r--r-- | net/netfilter/nf_conntrack_bpf.c | 66 |
1 files changed, 65 insertions, 1 deletions
diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c index 1cd87b28c9b0..77eb8e959f61 100644 --- a/net/netfilter/nf_conntrack_bpf.c +++ b/net/netfilter/nf_conntrack_bpf.c @@ -6,8 +6,10 @@ * are exposed through to BPF programs is explicitly unstable. */ +#include <linux/bpf_verifier.h> #include <linux/bpf.h> #include <linux/btf.h> +#include <linux/mutex.h> #include <linux/types.h> #include <linux/btf_ids.h> #include <linux/net_namespace.h> @@ -184,6 +186,54 @@ static struct nf_conn *__bpf_nf_ct_lookup(struct net *net, return ct; } +BTF_ID_LIST(btf_nf_conn_ids) +BTF_ID(struct, nf_conn) +BTF_ID(struct, nf_conn___init) + +/* Check writes into `struct nf_conn` */ +static int _nf_conntrack_btf_struct_access(struct bpf_verifier_log *log, + const struct btf *btf, + const struct btf_type *t, int off, + int size, enum bpf_access_type atype, + u32 *next_btf_id, + enum bpf_type_flag *flag) +{ + const struct btf_type *ncit; + const struct btf_type *nct; + size_t end; + + ncit = btf_type_by_id(btf, btf_nf_conn_ids[1]); + nct = btf_type_by_id(btf, btf_nf_conn_ids[0]); + + if (t != nct && t != ncit) { + bpf_log(log, "only read is supported\n"); + return -EACCES; + } + + /* `struct nf_conn` and `struct nf_conn___init` have the same layout + * so we are safe to simply merge offset checks here + */ + switch (off) { +#if defined(CONFIG_NF_CONNTRACK_MARK) + case offsetof(struct nf_conn, mark): + end = offsetofend(struct nf_conn, mark); + break; +#endif + default: + bpf_log(log, "no write support to nf_conn at off %d\n", off); + return -EACCES; + } + + if (off + size > end) { + bpf_log(log, + "write access at off %d with size %d beyond the member of nf_conn ended at %zu\n", + off, size, end); + return -EACCES; + } + + return 0; +} + __diag_push(); __diag_ignore_all("-Wmissing-prototypes", "Global functions as their definitions will be in nf_conntrack BTF"); @@ -449,5 +499,19 @@ int register_nf_conntrack_bpf(void) int ret; ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &nf_conntrack_kfunc_set); - return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &nf_conntrack_kfunc_set); + ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &nf_conntrack_kfunc_set); + if (!ret) { + mutex_lock(&nf_conn_btf_access_lock); + nfct_bsa = _nf_conntrack_btf_struct_access; + mutex_unlock(&nf_conn_btf_access_lock); + } + + return ret; +} + +void cleanup_nf_conntrack_bpf(void) +{ + mutex_lock(&nf_conn_btf_access_lock); + nfct_bsa = NULL; + mutex_unlock(&nf_conn_btf_access_lock); } |