From 1559b4aa1db443096af493c7d621dc156054babe Mon Sep 17 00:00:00 2001 From: Jakub Sitnicki Date: Fri, 17 Jul 2020 12:35:25 +0200 Subject: inet: Run SK_LOOKUP BPF program on socket lookup Run a BPF program before looking up a listening socket on the receive path. Program selects a listening socket to yield as result of socket lookup by calling bpf_sk_assign() helper and returning SK_PASS code. Program can revert its decision by assigning a NULL socket with bpf_sk_assign(). Alternatively, BPF program can also fail the lookup by returning with SK_DROP, or let the lookup continue as usual with SK_PASS on return, when no socket has been selected with bpf_sk_assign(). This lets the user match packets with listening sockets freely at the last possible point on the receive path, where we know that packets are destined for local delivery after undergoing policing, filtering, and routing. With BPF code selecting the socket, directing packets destined to an IP range or to a port range to a single socket becomes possible. In case multiple programs are attached, they are run in series in the order in which they were attached. The end result is determined from return codes of all the programs according to following rules: 1. If any program returned SK_PASS and selected a valid socket, the socket is used as result of socket lookup. 2. If more than one program returned SK_PASS and selected a socket, last selection takes effect. 3. If any program returned SK_DROP, and no program returned SK_PASS and selected a socket, socket lookup fails with -ECONNREFUSED. 4. If all programs returned SK_PASS and none of them selected a socket, socket lookup continues to htable-based lookup. Suggested-by: Marek Majkowski Signed-off-by: Jakub Sitnicki Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200717103536.397595-5-jakub@cloudflare.com --- kernel/bpf/net_namespace.c | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) (limited to 'kernel/bpf/net_namespace.c') diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c index 38b368bccda2..4e1bcaa2c3cb 100644 --- a/kernel/bpf/net_namespace.c +++ b/kernel/bpf/net_namespace.c @@ -25,6 +25,28 @@ struct bpf_netns_link { /* Protects updates to netns_bpf */ DEFINE_MUTEX(netns_bpf_mutex); +static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type) +{ + switch (type) { + case NETNS_BPF_SK_LOOKUP: + static_branch_dec(&bpf_sk_lookup_enabled); + break; + default: + break; + } +} + +static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type) +{ + switch (type) { + case NETNS_BPF_SK_LOOKUP: + static_branch_inc(&bpf_sk_lookup_enabled); + break; + default: + break; + } +} + /* Must be called with netns_bpf_mutex held. */ static void netns_bpf_run_array_detach(struct net *net, enum netns_bpf_attach_type type) @@ -91,6 +113,9 @@ static void bpf_netns_link_release(struct bpf_link *link) if (!net) goto out_unlock; + /* Mark attach point as unused */ + netns_bpf_attach_type_unneed(type); + /* Remember link position in case of safe delete */ idx = link_index(net, type, net_link); list_del(&net_link->node); @@ -428,6 +453,9 @@ static int netns_bpf_link_attach(struct net *net, struct bpf_link *link, lockdep_is_held(&netns_bpf_mutex)); bpf_prog_array_free(run_array); + /* Mark attach point as used */ + netns_bpf_attach_type_need(type); + out_unlock: mutex_unlock(&netns_bpf_mutex); return err; @@ -503,8 +531,10 @@ static void __net_exit netns_bpf_pernet_pre_exit(struct net *net) mutex_lock(&netns_bpf_mutex); for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) { netns_bpf_run_array_detach(net, type); - list_for_each_entry(net_link, &net->bpf.links[type], node) + list_for_each_entry(net_link, &net->bpf.links[type], node) { net_link->net = NULL; /* auto-detach link */ + netns_bpf_attach_type_unneed(type); + } if (net->bpf.progs[type]) bpf_prog_put(net->bpf.progs[type]); } -- cgit v1.2.3