LineageOS/android_packages_modules_Connectivity
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Merge "Move BPF offload program from netd to mainline" am: c26848e7bd

Browse Source 
Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1424189

Change-Id: Ia0b8a185f44dac7db365fcb9fc865a82bd552d62
This commit is contained in:
Nucca Chen
2020-09-18 04:27:28 +00:00
committed by Automerger Merge Worker
parent 8780ad918d 56c632caed
commit a0d6f9712b
3 changed files with 241 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
Tethering/apex/Android.bp
View File

@@ -19,6 +19,7 @@ apex {
updatable: true,
min_sdk_version: "current",
java_libs: ["framework-tethering"],
bpfs: ["offload.o"],
apps: ["Tethering"],
manifest: "manifest.json",
key: "com.android.tethering.key",

33
Tethering/bpf_progs/Android.bp Normal file
View File

@@ -0,0 +1,33 @@
//
// Copyright (C) 2020 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//
// bpf kernel programs
//
bpf {
name: "offload.o",
srcs: ["offload.c"],
cflags: [
"-Wall",
"-Werror",
],
include_dirs: [
// TODO: get rid of system/netd.
"system/netd/bpf_progs", // for bpf_net_helpers.h
"system/netd/libnetdbpf/include", // for bpf_shared.h
"system/netd/libnetdutils/include", // for UidConstants.h
],
}

207
Tethering/bpf_progs/offload.c Normal file
View File

@@ -0,0 +1,207 @@
/*
* Copyright (C) 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <linux/if.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/pkt_cls.h>
#include <linux/tcp.h>
#include "bpf_helpers.h"
#include "bpf_net_helpers.h"
#include "netdbpf/bpf_shared.h"
DEFINE_BPF_MAP_GRW(tether_ingress_map, HASH, TetherIngressKey, TetherIngressValue, 64,
AID_NETWORK_STACK)
// Tethering stats, indexed by upstream interface.
DEFINE_BPF_MAP_GRW(tether_stats_map, HASH, uint32_t, TetherStatsValue, 16, AID_NETWORK_STACK)
// Tethering data limit, indexed by upstream interface.
// (tethering allowed when stats[iif].rxBytes + stats[iif].txBytes < limit[iif])
DEFINE_BPF_MAP_GRW(tether_limit_map, HASH, uint32_t, uint64_t, 16, AID_NETWORK_STACK)
static inline __always_inline int do_forward(struct __sk_buff* skb, bool is_ethernet) {
int l2_header_size = is_ethernet ? sizeof(struct ethhdr) : 0;
void* data = (void*)(long)skb->data;
const void* data_end = (void*)(long)skb->data_end;
struct ethhdr* eth = is_ethernet ? data : NULL; // used iff is_ethernet
struct ipv6hdr* ip6 = is_ethernet ? (void*)(eth + 1) : data;
// Must be meta-ethernet IPv6 frame
if (skb->protocol != htons(ETH_P_IPV6)) return TC_ACT_OK;
// Must have (ethernet and) ipv6 header
if (data + l2_header_size + sizeof(*ip6) > data_end) return TC_ACT_OK;
// Ethertype - if present - must be IPv6
if (is_ethernet && (eth->h_proto != htons(ETH_P_IPV6))) return TC_ACT_OK;
// IP version must be 6
if (ip6->version != 6) return TC_ACT_OK;
// Cannot decrement during forward if already zero or would be zero,
// Let the kernel's stack handle these cases and generate appropriate ICMP errors.
if (ip6->hop_limit <= 1) return TC_ACT_OK;
// Protect against forwarding packets sourced from ::1 or fe80::/64 or other weirdness.
__be32 src32 = ip6->saddr.s6_addr32[0];
if (src32 != htonl(0x0064ff9b) && // 64:ff9b:/32 incl. XLAT464 WKP
(src32 & htonl(0xe0000000)) != htonl(0x20000000)) // 2000::/3 Global Unicast
return TC_ACT_OK;
TetherIngressKey k = {
.iif = skb->ifindex,
.neigh6 = ip6->daddr,
};
TetherIngressValue* v = bpf_tether_ingress_map_lookup_elem(&k);
// If we don't find any offload information then simply let the core stack handle it...
if (!v) return TC_ACT_OK;
uint32_t stat_and_limit_k = skb->ifindex;
TetherStatsValue* stat_v = bpf_tether_stats_map_lookup_elem(&stat_and_limit_k);
// If we don't have anywhere to put stats, then abort...
if (!stat_v) return TC_ACT_OK;
uint64_t* limit_v = bpf_tether_limit_map_lookup_elem(&stat_and_limit_k);
// If we don't have a limit, then abort...
if (!limit_v) return TC_ACT_OK;
// Required IPv6 minimum mtu is 1280, below that not clear what we should do, abort...
const int pmtu = v->pmtu;
if (pmtu < IPV6_MIN_MTU) return TC_ACT_OK;
// Approximate handling of TCP/IPv6 overhead for incoming LRO/GRO packets: default
// outbound path mtu of 1500 is not necessarily correct, but worst case we simply
// undercount, which is still better then not accounting for this overhead at all.
// Note: this really shouldn't be device/path mtu at all, but rather should be
// derived from this particular connection's mss (ie. from gro segment size).
// This would require a much newer kernel with newer ebpf accessors.
// (This is also blindly assuming 12 bytes of tcp timestamp option in tcp header)
uint64_t packets = 1;
uint64_t bytes = skb->len;
if (bytes > pmtu) {
const int tcp_overhead = sizeof(struct ipv6hdr) + sizeof(struct tcphdr) + 12;
const int mss = pmtu - tcp_overhead;
const uint64_t payload = bytes - tcp_overhead;
packets = (payload + mss - 1) / mss;
bytes = tcp_overhead * packets + payload;
}
// Are we past the limit? If so, then abort...
// Note: will not overflow since u64 is 936 years even at 5Gbps.
// Do not drop here. Offload is just that, whenever we fail to handle
// a packet we let the core stack deal with things.
// (The core stack needs to handle limits correctly anyway,
// since we don't offload all traffic in both directions)
if (stat_v->rxBytes + stat_v->txBytes + bytes > *limit_v) return TC_ACT_OK;
if (!is_ethernet) {
is_ethernet = true;
l2_header_size = sizeof(struct ethhdr);
// Try to inject an ethernet header, and simply return if we fail
if (bpf_skb_change_head(skb, l2_header_size, /*flags*/ 0)) {
__sync_fetch_and_add(&stat_v->rxErrors, 1);
return TC_ACT_OK;
}
// bpf_skb_change_head() invalidates all pointers - reload them
data = (void*)(long)skb->data;
data_end = (void*)(long)skb->data_end;
eth = data;
ip6 = (void*)(eth + 1);
// I do not believe this can ever happen, but keep the verifier happy...
if (data + l2_header_size + sizeof(*ip6) > data_end) {
__sync_fetch_and_add(&stat_v->rxErrors, 1);
return TC_ACT_SHOT;
}
};
// CHECKSUM_COMPLETE is a 16-bit one's complement sum,
// thus corrections for it need to be done in 16-byte chunks at even offsets.
// IPv6 nexthdr is at offset 6, while hop limit is at offset 7
uint8_t old_hl = ip6->hop_limit;
--ip6->hop_limit;
uint8_t new_hl = ip6->hop_limit;
// bpf_csum_update() always succeeds if the skb is CHECKSUM_COMPLETE and returns an error
// (-ENOTSUPP) if it isn't.
bpf_csum_update(skb, 0xFFFF - ntohs(old_hl) + ntohs(new_hl));
__sync_fetch_and_add(&stat_v->rxPackets, packets);
__sync_fetch_and_add(&stat_v->rxBytes, bytes);
// Overwrite any mac header with the new one
*eth = v->macHeader;
// Redirect to forwarded interface.
//
// Note that bpf_redirect() cannot fail unless you pass invalid flags.
// The redirect actually happens after the ebpf program has already terminated,
// and can fail for example for mtu reasons at that point in time, but there's nothing
// we can do about it here.
return bpf_redirect(v->oif, 0 /* this is effectively BPF_F_EGRESS */);
}
SEC("schedcls/ingress/tether_ether")
int sched_cls_ingress_tether_ether(struct __sk_buff* skb) {
return do_forward(skb, true);
}
// Note: section names must be unique to prevent programs from appending to each other,
// so instead the bpf loader will strip everything past the final $ symbol when actually
// pinning the program into the filesystem.
//
// bpf_skb_change_head() is only present on 4.14+ and 2 trivial kernel patches are needed:
// ANDROID: net: bpf: Allow TC programs to call BPF_FUNC_skb_change_head
// ANDROID: net: bpf: permit redirect from ingress L3 to egress L2 devices at near max mtu
// (the first of those has already been upstreamed)
//
// 5.4 kernel support was only added to Android Common Kernel in R,
// and thus a 5.4 kernel always supports this.
//
// Hence, this mandatory (must load successfully) implementation for 5.4+ kernels:
DEFINE_BPF_PROG_KVER("schedcls/ingress/tether_rawip$5_4", AID_ROOT, AID_ROOT,
sched_cls_ingress_tether_rawip_5_4, KVER(5, 4, 0))
(struct __sk_buff* skb) {
return do_forward(skb, false);
}
// and this identical optional (may fail to load) implementation for [4.14..5.4) patched kernels:
DEFINE_OPTIONAL_BPF_PROG_KVER_RANGE("schedcls/ingress/tether_rawip$4_14", AID_ROOT, AID_ROOT,
sched_cls_ingress_tether_rawip_4_14, KVER(4, 14, 0),
KVER(5, 4, 0))
(struct __sk_buff* skb) {
return do_forward(skb, false);
}
// and define a no-op stub for [4.9,4.14) and unpatched [4.14,5.4) kernels.
// (if the above real 4.14+ program loaded successfully, then bpfloader will have already pinned
// it at the same location this one would be pinned at and will thus skip loading this stub)
DEFINE_BPF_PROG_KVER_RANGE("schedcls/ingress/tether_rawip$stub", AID_ROOT, AID_ROOT,
sched_cls_ingress_tether_rawip_stub, KVER_NONE, KVER(5, 4, 0))
(struct __sk_buff* skb) {
return TC_ACT_OK;
}
LICENSE("Apache 2.0");
CRITICAL("netd");