bpf_progs/dscpPolicy.c - android_packages_modules_Connectivity - Gitiles

 /*
  * Copyright (C) 2021 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/bpf.h>
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/pkt_cls.h>
 #include <linux/tcp.h>
 #include <linux/types.h>
 #include <netinet/in.h>
 #include <netinet/udp.h>
 #include <stdint.h>
 #include <string.h>

 // The resulting .o needs to load on the Android T bpfloader
 #define BPFLOADER_MIN_VER BPFLOADER_T_VERSION

 #include "bpf_helpers.h"
 #include "dscpPolicy.h"

 #define ECN_MASK 3
 #define IP4_OFFSET(field, header) ((header) + offsetof(struct iphdr, field))
 #define UPDATE_TOS(dscp, tos) ((dscp) << 2) | ((tos) & ECN_MASK)

 DEFINE_BPF_MAP_GRW(socket_policy_cache_map, HASH, uint64_t, RuleEntry, CACHE_MAP_SIZE, AID_SYSTEM)

 DEFINE_BPF_MAP_GRW(ipv4_dscp_policies_map, ARRAY, uint32_t, DscpPolicy, MAX_POLICIES, AID_SYSTEM)
 DEFINE_BPF_MAP_GRW(ipv6_dscp_policies_map, ARRAY, uint32_t, DscpPolicy, MAX_POLICIES, AID_SYSTEM)

 static inline __always_inline void match_policy(struct __sk_buff* skb, bool ipv4) {
     void* data = (void*)(long)skb->data;
     const void* data_end = (void*)(long)skb->data_end;

     const int l2_header_size = sizeof(struct ethhdr);
     struct ethhdr* eth = data;

     if (data + l2_header_size > data_end) return;

     int hdr_size = 0;

     // used for map lookup
     uint64_t cookie = bpf_get_socket_cookie(skb);
     if (!cookie) return;

     __be16 sport = 0;
     uint16_t dport = 0;
     uint8_t protocol = 0;  // TODO: Use are reserved value? Or int (-1) and cast to uint below?
     struct in6_addr src_ip = {};
     struct in6_addr dst_ip = {};
     uint8_t tos = 0;            // Only used for IPv4
     __be32 old_first_be32 = 0;  // Only used for IPv6
     if (ipv4) {
         const struct iphdr* const iph = (void*)(eth + 1);
         hdr_size = l2_header_size + sizeof(struct iphdr);
         // Must have ipv4 header
         if (data + hdr_size > data_end) return;

         // IP version must be 4
         if (iph->version != 4) return;

         // We cannot handle IP options, just standard 20 byte == 5 dword minimal IPv4 header
         if (iph->ihl != 5) return;

         // V4 mapped address in in6_addr sets 10/11 position to 0xff.
         src_ip.s6_addr32[2] = htonl(0x0000ffff);
         dst_ip.s6_addr32[2] = htonl(0x0000ffff);

         // Copy IPv4 address into in6_addr for easy comparison below.
         src_ip.s6_addr32[3] = iph->saddr;
         dst_ip.s6_addr32[3] = iph->daddr;
         protocol = iph->protocol;
         tos = iph->tos;
     } else {
         struct ipv6hdr* ip6h = (void*)(eth + 1);
         hdr_size = l2_header_size + sizeof(struct ipv6hdr);
         // Must have ipv6 header
         if (data + hdr_size > data_end) return;

         if (ip6h->version != 6) return;

         src_ip = ip6h->saddr;
         dst_ip = ip6h->daddr;
         protocol = ip6h->nexthdr;
         old_first_be32 = *(__be32*)ip6h;
     }

     switch (protocol) {
         case IPPROTO_UDP:
         case IPPROTO_UDPLITE: {
             struct udphdr* udp;
             udp = data + hdr_size;
             if ((void*)(udp + 1) > data_end) return;
             sport = udp->source;
             dport = ntohs(udp->dest);
         } break;
         case IPPROTO_TCP: {
             struct tcphdr* tcp;
             tcp = data + hdr_size;
             if ((void*)(tcp + 1) > data_end) return;
             sport = tcp->source;
             dport = ntohs(tcp->dest);
         } break;
         default:
             return;
     }

     RuleEntry* existing_rule = bpf_socket_policy_cache_map_lookup_elem(&cookie);

     if (existing_rule &&
         v6_equal(src_ip, existing_rule->src_ip) &&
         v6_equal(dst_ip, existing_rule->dst_ip) &&
         skb->ifindex == existing_rule->ifindex &&
         sport == existing_rule->src_port &&
         dport == existing_rule->dst_port &&
         protocol == existing_rule->proto) {
         if (existing_rule->dscp_val < 0) return;
         if (ipv4) {
             uint8_t newTos = UPDATE_TOS(existing_rule->dscp_val, tos);
             bpf_l3_csum_replace(skb, IP4_OFFSET(check, l2_header_size), htons(tos), htons(newTos),
                                 sizeof(uint16_t));
             bpf_skb_store_bytes(skb, IP4_OFFSET(tos, l2_header_size), &newTos, sizeof(newTos), 0);
         } else {
             __be32 new_first_be32 =
                 htonl(ntohl(old_first_be32) & 0xF03FFFFF | (existing_rule->dscp_val << 22));
             bpf_skb_store_bytes(skb, l2_header_size, &new_first_be32, sizeof(__be32),
                 BPF_F_RECOMPUTE_CSUM);
         }
         return;
     }

     // Linear scan ipv4_dscp_policies_map since no stored params match skb.
     int best_score = 0;
     int8_t new_dscp = -1;

     for (register uint64_t i = 0; i < MAX_POLICIES; i++) {
         // Using a uint64 in for loop prevents infinite loop during BPF load,
         // but the key is uint32, so convert back.
         uint32_t key = i;

         DscpPolicy* policy;
         if (ipv4) {
             policy = bpf_ipv4_dscp_policies_map_lookup_elem(&key);
         } else {
             policy = bpf_ipv6_dscp_policies_map_lookup_elem(&key);
         }

         // If the policy lookup failed, just continue (this should not ever happen)
         if (!policy) continue;

         // If policy iface index does not match skb, then skip to next policy.
         if (policy->ifindex != skb->ifindex) continue;

         int score = 0;

         if (policy->present_fields & PROTO_MASK_FLAG) {
             if (protocol != policy->proto) continue;
             score += 0xFFFF;
         }
         if (policy->present_fields & SRC_IP_MASK_FLAG) {
             if (v6_not_equal(src_ip, policy->src_ip)) continue;
             score += 0xFFFF;
         }
         if (policy->present_fields & DST_IP_MASK_FLAG) {
             if (v6_not_equal(dst_ip, policy->dst_ip)) continue;
             score += 0xFFFF;
         }
         if (policy->present_fields & SRC_PORT_MASK_FLAG) {
             if (sport != policy->src_port) continue;
             score += 0xFFFF;
         }
         if (dport < policy->dst_port_start) continue;
         if (dport > policy->dst_port_end) continue;
         score += 0xFFFF + policy->dst_port_start - policy->dst_port_end;

         if (score > best_score) {
             best_score = score;
             new_dscp = policy->dscp_val;
         }
     }

     RuleEntry value = {
         .src_ip = src_ip,
         .dst_ip = dst_ip,
         .ifindex = skb->ifindex,
         .src_port = sport,
         .dst_port = dport,
         .proto = protocol,
         .dscp_val = new_dscp,
     };

     // Update cache with found policy.
     bpf_socket_policy_cache_map_update_elem(&cookie, &value, BPF_ANY);

     if (new_dscp < 0) return;

     // Need to store bytes after updating map or program will not load.
     if (ipv4) {
         uint8_t new_tos = UPDATE_TOS(new_dscp, tos);
         bpf_l3_csum_replace(skb, IP4_OFFSET(check, l2_header_size), htons(tos), htons(new_tos), 2);
         bpf_skb_store_bytes(skb, IP4_OFFSET(tos, l2_header_size), &new_tos, sizeof(new_tos), 0);
     } else {
         __be32 new_first_be32 = htonl(ntohl(old_first_be32) & 0xF03FFFFF | (new_dscp << 22));
         bpf_skb_store_bytes(skb, l2_header_size, &new_first_be32, sizeof(__be32),
             BPF_F_RECOMPUTE_CSUM);
     }
     return;
 }

 DEFINE_BPF_PROG_KVER("schedcls/set_dscp_ether", AID_ROOT, AID_SYSTEM, schedcls_set_dscp_ether,
                      KVER_5_15)
 (struct __sk_buff* skb) {
     if (skb->pkt_type != PACKET_HOST) return TC_ACT_PIPE;

     if (skb->protocol == htons(ETH_P_IP)) {
         match_policy(skb, true);
     } else if (skb->protocol == htons(ETH_P_IPV6)) {
         match_policy(skb, false);
     }

     // Always return TC_ACT_PIPE
     return TC_ACT_PIPE;
 }

 LICENSE("Apache 2.0");
 CRITICAL("Connectivity");
 DISABLE_BTF_ON_USER_BUILDS();
	/*
	* Copyright (C) 2021 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/bpf.h>
	#include <linux/if_ether.h>
	#include <linux/if_packet.h>
	#include <linux/ip.h>
	#include <linux/ipv6.h>
	#include <linux/pkt_cls.h>
	#include <linux/tcp.h>
	#include <linux/types.h>
	#include <netinet/in.h>
	#include <netinet/udp.h>
	#include <stdint.h>
	#include <string.h>

	// The resulting .o needs to load on the Android T bpfloader
	#define BPFLOADER_MIN_VER BPFLOADER_T_VERSION

	#include "bpf_helpers.h"
	#include "dscpPolicy.h"

	#define ECN_MASK 3
	#define IP4_OFFSET(field, header) ((header) + offsetof(struct iphdr, field))
	#define UPDATE_TOS(dscp, tos) ((dscp) << 2) \| ((tos) & ECN_MASK)

	DEFINE_BPF_MAP_GRW(socket_policy_cache_map, HASH, uint64_t, RuleEntry, CACHE_MAP_SIZE, AID_SYSTEM)

	DEFINE_BPF_MAP_GRW(ipv4_dscp_policies_map, ARRAY, uint32_t, DscpPolicy, MAX_POLICIES, AID_SYSTEM)
	DEFINE_BPF_MAP_GRW(ipv6_dscp_policies_map, ARRAY, uint32_t, DscpPolicy, MAX_POLICIES, AID_SYSTEM)

	static inline __always_inline void match_policy(struct __sk_buff* skb, bool ipv4) {
	void* data = (void*)(long)skb->data;
	const void* data_end = (void*)(long)skb->data_end;

	const int l2_header_size = sizeof(struct ethhdr);
	struct ethhdr* eth = data;

	if (data + l2_header_size > data_end) return;

	int hdr_size = 0;

	// used for map lookup
	uint64_t cookie = bpf_get_socket_cookie(skb);
	if (!cookie) return;

	__be16 sport = 0;
	uint16_t dport = 0;
	uint8_t protocol = 0; // TODO: Use are reserved value? Or int (-1) and cast to uint below?
	struct in6_addr src_ip = {};
	struct in6_addr dst_ip = {};
	uint8_t tos = 0; // Only used for IPv4
	__be32 old_first_be32 = 0; // Only used for IPv6
	if (ipv4) {
	const struct iphdr* const iph = (void*)(eth + 1);
	hdr_size = l2_header_size + sizeof(struct iphdr);
	// Must have ipv4 header
	if (data + hdr_size > data_end) return;

	// IP version must be 4
	if (iph->version != 4) return;

	// We cannot handle IP options, just standard 20 byte == 5 dword minimal IPv4 header
	if (iph->ihl != 5) return;

	// V4 mapped address in in6_addr sets 10/11 position to 0xff.
	src_ip.s6_addr32[2] = htonl(0x0000ffff);
	dst_ip.s6_addr32[2] = htonl(0x0000ffff);

	// Copy IPv4 address into in6_addr for easy comparison below.
	src_ip.s6_addr32[3] = iph->saddr;
	dst_ip.s6_addr32[3] = iph->daddr;
	protocol = iph->protocol;
	tos = iph->tos;
	} else {
	struct ipv6hdr* ip6h = (void*)(eth + 1);
	hdr_size = l2_header_size + sizeof(struct ipv6hdr);
	// Must have ipv6 header
	if (data + hdr_size > data_end) return;

	if (ip6h->version != 6) return;

	src_ip = ip6h->saddr;
	dst_ip = ip6h->daddr;
	protocol = ip6h->nexthdr;
	old_first_be32 = (__be32)ip6h;
	}

	switch (protocol) {
	case IPPROTO_UDP:
	case IPPROTO_UDPLITE: {
	struct udphdr* udp;
	udp = data + hdr_size;
	if ((void*)(udp + 1) > data_end) return;
	sport = udp->source;
	dport = ntohs(udp->dest);
	} break;
	case IPPROTO_TCP: {
	struct tcphdr* tcp;
	tcp = data + hdr_size;
	if ((void*)(tcp + 1) > data_end) return;
	sport = tcp->source;
	dport = ntohs(tcp->dest);
	} break;
	default:
	return;
	}

	RuleEntry* existing_rule = bpf_socket_policy_cache_map_lookup_elem(&cookie);

	if (existing_rule &&
	v6_equal(src_ip, existing_rule->src_ip) &&
	v6_equal(dst_ip, existing_rule->dst_ip) &&
	skb->ifindex == existing_rule->ifindex &&
	sport == existing_rule->src_port &&
	dport == existing_rule->dst_port &&
	protocol == existing_rule->proto) {
	if (existing_rule->dscp_val < 0) return;
	if (ipv4) {
	uint8_t newTos = UPDATE_TOS(existing_rule->dscp_val, tos);
	bpf_l3_csum_replace(skb, IP4_OFFSET(check, l2_header_size), htons(tos), htons(newTos),
	sizeof(uint16_t));
	bpf_skb_store_bytes(skb, IP4_OFFSET(tos, l2_header_size), &newTos, sizeof(newTos), 0);
	} else {
	__be32 new_first_be32 =
	htonl(ntohl(old_first_be32) & 0xF03FFFFF \| (existing_rule->dscp_val << 22));
	bpf_skb_store_bytes(skb, l2_header_size, &new_first_be32, sizeof(__be32),
	BPF_F_RECOMPUTE_CSUM);
	}
	return;
	}

	// Linear scan ipv4_dscp_policies_map since no stored params match skb.
	int best_score = 0;
	int8_t new_dscp = -1;

	for (register uint64_t i = 0; i < MAX_POLICIES; i++) {
	// Using a uint64 in for loop prevents infinite loop during BPF load,
	// but the key is uint32, so convert back.
	uint32_t key = i;

	DscpPolicy* policy;
	if (ipv4) {
	policy = bpf_ipv4_dscp_policies_map_lookup_elem(&key);
	} else {
	policy = bpf_ipv6_dscp_policies_map_lookup_elem(&key);
	}

	// If the policy lookup failed, just continue (this should not ever happen)
	if (!policy) continue;

	// If policy iface index does not match skb, then skip to next policy.
	if (policy->ifindex != skb->ifindex) continue;

	int score = 0;

	if (policy->present_fields & PROTO_MASK_FLAG) {
	if (protocol != policy->proto) continue;
	score += 0xFFFF;
	}
	if (policy->present_fields & SRC_IP_MASK_FLAG) {
	if (v6_not_equal(src_ip, policy->src_ip)) continue;
	score += 0xFFFF;
	}
	if (policy->present_fields & DST_IP_MASK_FLAG) {
	if (v6_not_equal(dst_ip, policy->dst_ip)) continue;
	score += 0xFFFF;
	}
	if (policy->present_fields & SRC_PORT_MASK_FLAG) {
	if (sport != policy->src_port) continue;
	score += 0xFFFF;
	}
	if (dport < policy->dst_port_start) continue;
	if (dport > policy->dst_port_end) continue;
	score += 0xFFFF + policy->dst_port_start - policy->dst_port_end;

	if (score > best_score) {
	best_score = score;
	new_dscp = policy->dscp_val;
	}
	}

	RuleEntry value = {
	.src_ip = src_ip,
	.dst_ip = dst_ip,
	.ifindex = skb->ifindex,
	.src_port = sport,
	.dst_port = dport,
	.proto = protocol,
	.dscp_val = new_dscp,
	};

	// Update cache with found policy.
	bpf_socket_policy_cache_map_update_elem(&cookie, &value, BPF_ANY);

	if (new_dscp < 0) return;

	// Need to store bytes after updating map or program will not load.
	if (ipv4) {
	uint8_t new_tos = UPDATE_TOS(new_dscp, tos);
	bpf_l3_csum_replace(skb, IP4_OFFSET(check, l2_header_size), htons(tos), htons(new_tos), 2);
	bpf_skb_store_bytes(skb, IP4_OFFSET(tos, l2_header_size), &new_tos, sizeof(new_tos), 0);
	} else {
	__be32 new_first_be32 = htonl(ntohl(old_first_be32) & 0xF03FFFFF \| (new_dscp << 22));
	bpf_skb_store_bytes(skb, l2_header_size, &new_first_be32, sizeof(__be32),
	BPF_F_RECOMPUTE_CSUM);
	}
	return;
	}

	DEFINE_BPF_PROG_KVER("schedcls/set_dscp_ether", AID_ROOT, AID_SYSTEM, schedcls_set_dscp_ether,
	KVER_5_15)
	(struct __sk_buff* skb) {
	if (skb->pkt_type != PACKET_HOST) return TC_ACT_PIPE;

	if (skb->protocol == htons(ETH_P_IP)) {
	match_policy(skb, true);
	} else if (skb->protocol == htons(ETH_P_IPV6)) {
	match_policy(skb, false);
	}

	// Always return TC_ACT_PIPE
	return TC_ACT_PIPE;
	}

	LICENSE("Apache 2.0");
	CRITICAL("Connectivity");
	DISABLE_BTF_ON_USER_BUILDS();