[PATCH bpf-next v2 07/11] bpf, sockmap: Return socket cookie on lookup from syscall
From: Jakub Sitnicki <jakub@cloudflare.com>
Date: 2020-01-10 10:50:49
Also in:
bpf
Subsystem:
bpf [l7 framework] (sockmap), networking [general], networking [sockets], the rest · Maintainers:
John Fastabend, Jakub Sitnicki, Jiayuan Chen, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds
Tooling that populates the SOCKMAP with sockets from user-space needs a way to inspect its contents. Returning the struct sock * that SOCKMAP holds to user-space is neither safe nor useful. An approach established by REUSEPORT_SOCKARRAY is to return a socket cookie (a unique identifier) instead. Since socket cookies are u64 values SOCKMAP needs to support such a value size for lookup to be possible. This requires special handling on update, though. Attempts to do a lookup on SOCKMAP holding u32 values will be met with ENOSPC error. Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> --- net/core/sock_map.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index d1a91e41ff82..3731191a7d1e 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c@@ -10,6 +10,7 @@ #include <linux/skmsg.h> #include <linux/list.h> #include <linux/jhash.h> +#include <linux/sock_diag.h> struct bpf_stab { struct bpf_map map;
@@ -31,7 +32,8 @@ static struct bpf_map *sock_map_alloc(union bpf_attr *attr) return ERR_PTR(-EPERM); if (attr->max_entries == 0 || attr->key_size != 4 || - attr->value_size != 4 || + (attr->value_size != sizeof(u32) && + attr->value_size != sizeof(u64)) || attr->map_flags & ~SOCK_CREATE_FLAG_MASK) return ERR_PTR(-EINVAL);
@@ -298,6 +300,23 @@ static void *sock_map_lookup(struct bpf_map *map, void *key) return ERR_PTR(-EOPNOTSUPP); } +static void *sock_map_lookup_sys(struct bpf_map *map, void *key) +{ + struct sock *sk; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + if (map->value_size != sizeof(u64)) + return ERR_PTR(-ENOSPC); + + sk = __sock_map_lookup_elem(map, *(u32 *)key); + if (!sk) + return ERR_PTR(-ENOENT); + + sock_gen_cookie(sk); + return &sk->sk_cookie; +} + static int __sock_map_delete(struct bpf_stab *stab, struct sock *sk_test, struct sock **psk) {
@@ -448,12 +467,19 @@ static bool sock_map_redirect_okay(const struct sock *sk) static int sock_map_update_elem(struct bpf_map *map, void *key, void *value, u64 flags) { - u32 ufd = *(u32 *)value; u32 idx = *(u32 *)key; struct socket *sock; struct sock *sk; + u64 ufd; int ret; + if (map->value_size == sizeof(u64)) + ufd = *(u64 *)value; + else + ufd = *(u32 *)value; + if (ufd > S32_MAX) + return -EINVAL; + sock = sockfd_lookup(ufd, &ret); if (!sock) return ret;
@@ -562,6 +588,7 @@ const struct bpf_map_ops sock_map_ops = { .map_alloc = sock_map_alloc, .map_free = sock_map_free, .map_get_next_key = sock_map_get_next_key, + .map_lookup_elem_sys_only = sock_map_lookup_sys, .map_update_elem = sock_map_update_elem, .map_delete_elem = sock_map_delete_elem, .map_lookup_elem = sock_map_lookup,
--
2.24.1