[PATCH bpf-next v5 5/7] tools: bpftool: print netfilter link info

Florian Westphal
2023-04-21T17:04:07Z

Dump protocol family, hook and priority value:
$ bpftool link
2: netfilter prog 14
ip input prio -128
pids install(3264)
5: netfilter prog 14
ip6 forward prio 21
pids a.out(3387)
9: netfilter prog 14
ip prerouting prio 123
pids a.out(5700)
10: netfilter prog 14
ip input prio 21
pids test2(5701)

v2: Quentin Monnet suggested to also add 'bpftool net' support:

$ bpftool net
xdp:

tc:

flow_dissector:

netfilter:

ip prerouting prio 21 prog_id 14
ip input prio -128 prog_id 14
ip input prio 21 prog_id 14
ip forward prio 21 prog_id 14
ip output prio 21 prog_id 14
ip postrouting prio 21 prog_id 14

'bpftool net' only dumps netfilter link type, links are sorted by protocol
family, hook and priority.

v5: fix bpf ci failure: libbpf needs small update to prog_type_name[]
and probe_prog_load helper.
v4: don't fail with -EOPNOTSUPP in libbpf probe_prog_load, update
prog_type_name[] with "netfilter" entry (bpf ci)
v3: fix bpf.h copy, 'reserved' member was removed (Alexei)
use p_err, not fprintf (Quentin)

Suggested-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/eeeaac99-9053-90c2-aa33-cc1ecb1ae9ca@isovalent.com/
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
v5: libbpf needs small update to prog_type_name[] and probe_prog_load helper

tools/bpf/bpftool/link.c | 83 ++++++++++++++++++++++++++
tools/bpf/bpftool/main.h | 3 +
tools/bpf/bpftool/net.c | 106 +++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 14 +++++
tools/lib/bpf/libbpf.c | 3 +
tools/lib/bpf/libbpf_probes.c | 1 +
6 files changed, 210 insertions(+)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index f985b79cca27..d98dbc50cf4c 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -3,6 +3,8 @@

#include <errno.h>
#include <linux/err.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_arp.h>
#include <net/if.h>
#include <stdio.h>
#include <unistd.h>
@@ -135,6 +137,18 @@ static void show_iter_json(struct bpf_link_info *info, json_writer_t *wtr)
}
}

+void netfilter_dump_json(const struct bpf_link_info *info, json_writer_t *wtr)
+{
+ jsonw_uint_field(json_wtr, "pf",
+ info->netfilter.pf);
+ jsonw_uint_field(json_wtr, "hook",
+ info->netfilter.hooknum);
+ jsonw_int_field(json_wtr, "prio",
+ info->netfilter.priority);
+ jsonw_uint_field(json_wtr, "flags",
+ info->netfilter.flags);
+}
+
static int get_prog_info(int prog_id, struct bpf_prog_info *info)
{
__u32 len = sizeof(*info);
@@ -195,6 +209,10 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
info->netns.netns_ino);
show_link_attach_type_json(info->netns.attach_type, json_wtr);
break;
+ case BPF_LINK_TYPE_NETFILTER:
+ netfilter_dump_json(info, json_wtr);
+ break;
+
default:
break;
}
@@ -263,6 +281,68 @@ static void show_iter_plain(struct bpf_link_info *info)
}
}

+static const char * const pf2name[] = {
+ [NFPROTO_INET] = "inet",
+ [NFPROTO_IPV4] = "ip",
+ [NFPROTO_ARP] = "arp",
+ [NFPROTO_NETDEV] = "netdev",
+ [NFPROTO_BRIDGE] = "bridge",
+ [NFPROTO_IPV6] = "ip6",
+};
+
+static const char * const inethook2name[] = {
+ [NF_INET_PRE_ROUTING] = "prerouting",
+ [NF_INET_LOCAL_IN] = "input",
+ [NF_INET_FORWARD] = "forward",
+ [NF_INET_LOCAL_OUT] = "output",
+ [NF_INET_POST_ROUTING] = "postrouting",
+};
+
+static const char * const arphook2name[] = {
+ [NF_ARP_IN] = "input",
+ [NF_ARP_OUT] = "output",
+};
+
+void netfilter_dump_plain(const struct bpf_link_info *info)
+{
+ const char *hookname = NULL, *pfname = NULL;
+ unsigned int hook = info->netfilter.hooknum;
+ unsigned int pf = info->netfilter.pf;
+
+ if (pf < ARRAY_SIZE(pf2name))
+ pfname = pf2name[pf];
+
+ switch (pf) {
+ case NFPROTO_BRIDGE: /* bridge shares numbers with enum nf_inet_hooks */
+ case NFPROTO_IPV4:
+ case NFPROTO_IPV6:
+ case NFPROTO_INET:
+ if (hook < ARRAY_SIZE(inethook2name))
+ hookname = inethook2name[hook];
+ break;
+ case NFPROTO_ARP:
+ if (hook < ARRAY_SIZE(arphook2name))
+ hookname = arphook2name[hook];
+ default:
+ break;
+ }
+
+ if (pfname)
+ printf("\n\t%s", pfname);
+ else
+ printf("\n\tpf: %d", pf);
+
+ if (hookname)
+ printf(" %s", hookname);
+ else
+ printf(", hook %u,", hook);
+
+ printf(" prio %d", info->netfilter.priority);
+
+ if (info->netfilter.flags)
+ printf(" flags 0x%x", info->netfilter.flags);
+}
+
static int show_link_close_plain(int fd, struct bpf_link_info *info)
{
struct bpf_prog_info prog_info;
@@ -301,6 +381,9 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
printf("\n\tnetns_ino %u ", info->netns.netns_ino);
show_link_attach_type_plain(info->netns.attach_type);
break;
+ case BPF_LINK_TYPE_NETFILTER:
+ netfilter_dump_plain(info);
+ break;
default:
break;
}
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 00d11ca6d3f2..63d9aa1012a9 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -264,4 +264,7 @@ static inline bool hashmap__empty(struct hashmap *map)
return map ? hashmap__size(map) == 0 : true;
}

+/* print netfilter bpf_link info */
+void netfilter_dump_plain(const struct bpf_link_info *info);
+void netfilter_dump_json(const struct bpf_link_info *info, json_writer_t *wtr);
#endif
diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
index c40e44c938ae..26a49965bf71 100644
--- a/tools/bpf/bpftool/net.c
+++ b/tools/bpf/bpftool/net.c
@@ -647,6 +647,108 @@ static int do_detach(int argc, char **argv)
return 0;
}

+static int netfilter_link_compar(const void *a, const void *b)
+{
+ const struct bpf_link_info *nfa = a;
+ const struct bpf_link_info *nfb = b;
+ int delta;
+
+ delta = nfa->netfilter.pf - nfb->netfilter.pf;
+ if (delta)
+ return delta;
+
+ delta = nfa->netfilter.hooknum - nfb->netfilter.hooknum;
+ if (delta)
+ return delta;
+
+ if (nfa->netfilter.priority < nfb->netfilter.priority)
+ return -1;
+ if (nfa->netfilter.priority > nfb->netfilter.priority)
+ return 1;
+
+ return nfa->netfilter.flags - nfb->netfilter.flags;
+}
+
+static void show_link_netfilter(void)
+{
+ unsigned int nf_link_len = 0, nf_link_count = 0;
+ struct bpf_link_info *nf_link_info = NULL;
+ __u32 id = 0;
+
+ while (true) {
+ struct bpf_link_info info;
+ int fd, err;
+ __u32 len;
+
+ err = bpf_link_get_next_id(id, &id);
+ if (err) {
+ if (errno == ENOENT)
+ break;
+ p_err("can't get next link: %s (id %d)", strerror(errno), id);
+ break;
+ }
+
+ fd = bpf_link_get_fd_by_id(id);
+ if (fd < 0) {
+ p_err("can't get link by id (%u): %s", id, strerror(errno));
+ continue;
+ }
+
+ memset(&info, 0, sizeof(info));
+ len = sizeof(info);
+
+ err = bpf_link_get_info_by_fd(fd, &info, &len);
+
+ close(fd);
+
+ if (err) {
+ p_err("can't get link info for fd %d: %s", fd, strerror(errno));
+ continue;
+ }
+
+ if (info.type != BPF_LINK_TYPE_NETFILTER)
+ continue;
+
+ if (nf_link_count >= nf_link_len) {
+ static const unsigned int max_link_count = INT_MAX / sizeof(info);
+ struct bpf_link_info *expand;
+
+ if (nf_link_count > max_link_count) {
+ p_err("cannot handle more than %u links\n", max_link_count);
+ break;
+ }
+
+ nf_link_len += 16;
+
+ expand = realloc(nf_link_info, nf_link_len * sizeof(info));
+ if (!expand) {
+ p_err("realloc: %s", strerror(errno));
+ break;
+ }
+
+ nf_link_info = expand;
+ }
+
+ nf_link_info[nf_link_count] = info;
+ nf_link_count++;
+ }
+
+ qsort(nf_link_info, nf_link_count, sizeof(*nf_link_info), netfilter_link_compar);
+
+ for (id = 0; id < nf_link_count; id++) {
+ NET_START_OBJECT;
+ if (json_output)
+ netfilter_dump_json(&nf_link_info[id], json_wtr);
+ else
+ netfilter_dump_plain(&nf_link_info[id]);
+
+ NET_DUMP_UINT("id", " prog_id %u", nf_link_info[id].prog_id);
+ NET_END_OBJECT;
+ }
+
+ free(nf_link_info);
+}
+
static int do_show(int argc, char **argv)
{
struct bpf_attach_info attach_info = {};
@@ -701,6 +803,10 @@ static int do_show(int argc, char **argv)
NET_DUMP_UINT("id", "id %u", attach_info.flow_dissector_id);
NET_END_ARRAY("\n");

+ NET_START_ARRAY("netfilter", "%s:\n");
+ show_link_netfilter();
+ NET_END_ARRAY("\n");
+
NET_END_OBJECT;
if (json_output)
jsonw_end_array(json_wtr);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 4b20a7269bee..1bb11a6ee667 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -986,6 +986,7 @@ enum bpf_prog_type {
BPF_PROG_TYPE_LSM,
BPF_PROG_TYPE_SK_LOOKUP,
BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
+ BPF_PROG_TYPE_NETFILTER,
};

enum bpf_attach_type {
@@ -1050,6 +1051,7 @@ enum bpf_link_type {
BPF_LINK_TYPE_PERF_EVENT = 7,
BPF_LINK_TYPE_KPROBE_MULTI = 8,
BPF_LINK_TYPE_STRUCT_OPS = 9,
+ BPF_LINK_TYPE_NETFILTER = 10,

MAX_BPF_LINK_TYPE,
};
@@ -1560,6 +1562,12 @@ union bpf_attr {
*/
__u64 cookie;
} tracing;
+ struct {
+ __u32 pf;
+ __u32 hooknum;
+ __s32 priority;
+ __u32 flags;
+ } netfilter;
};
} link_create;

@@ -6410,6 +6418,12 @@ struct bpf_link_info {
struct {
__u32 map_id;
} struct_ops;
+ struct {
+ __u32 pf;
+ __u32 hooknum;
+ __s32 priority;
+ __u32 flags;
+ } netfilter;
};
} __attribute__((aligned(8)));

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2600d8384252..1cbacf9e71f3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -130,6 +130,7 @@ static const char * const link_type_name[] = {
[BPF_LINK_TYPE_PERF_EVENT] = "perf_event",
[BPF_LINK_TYPE_KPROBE_MULTI] = "kprobe_multi",
[BPF_LINK_TYPE_STRUCT_OPS] = "struct_ops",
+ [BPF_LINK_TYPE_NETFILTER] = "netfilter",
};

static const char * const map_type_name[] = {
@@ -201,6 +202,7 @@ static const char * const prog_type_name[] = {
[BPF_PROG_TYPE_LSM] = "lsm",
[BPF_PROG_TYPE_SK_LOOKUP] = "sk_lookup",
[BPF_PROG_TYPE_SYSCALL] = "syscall",
+ [BPF_PROG_TYPE_NETFILTER] = "netfilter",
};

static int __base_pr(enum libbpf_print_level level, const char *format,
@@ -8710,6 +8712,7 @@ static const struct bpf_sec_def section_defs[] = {
SEC_DEF("struct_ops+", STRUCT_OPS, 0, SEC_NONE),
SEC_DEF("struct_ops.s+", STRUCT_OPS, 0, SEC_SLEEPABLE),
SEC_DEF("sk_lookup", SK_LOOKUP, BPF_SK_LOOKUP, SEC_ATTACHABLE),
+ SEC_DEF("netfilter", NETFILTER, 0, SEC_NONE),
};

static size_t custom_sec_def_cnt;
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 4f3bc968ff8e..6065f408a59c 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -180,6 +180,7 @@ static int probe_prog_load(enum bpf_prog_type prog_type,
case BPF_PROG_TYPE_SK_REUSEPORT:
case BPF_PROG_TYPE_FLOW_DISSECTOR:
case BPF_PROG_TYPE_CGROUP_SYSCTL:
+ case BPF_PROG_TYPE_NETFILTER:
break;
default:
return -EOPNOTSUPP;
--
2.39.2