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[原创][eBPF源码分析]Socket_filter类型调用链埋点分析
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发表于: 2024-5-11 18:51
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socket filter，在BPF中的类型为BPF_PROG_TYPE_SOCKET_FILTER，顾名思义，实现的是socket的过滤器。
本文会分析BPF_PROG_TYPE_SOCKET_FILTER类型程序的实现原理，一直到埋点函数。
内核中有示例代码，位置在sample/bpf/sock_example.c、samples/bpf/sockex1_kern.c等。
一般会将socket filter程序的段名定义成SEC("socketxxx")
下文的代码分析，基于5.15.99版本的内核
这里通过sample/bpf/sock_example.c学习。
一些注释和文件头
加载map，使用内核的bpf_create_map函数
用字节码的形式定义的BPF prog程序本体
这里的bpf_insn是bpf程序底层的字节码，是抽象过的汇编代码。各种高级库都要转换成这种形式，最后转换成汇编代码。
以上实现的程序：
用内核函数bpf_load_program装载prog程序，参数为BPF_PROG_TYPE_SOCKET_FILTER，表示socket/filter类型
open_raw_sock创建一个raw_socket，调用setsockopt将bpf prog附着到这个socket上，参数为SO_ATTACH_BPF。
接下来重点关注setsockopt如何访问sock/filter的点位。
查找setsockopt的源码，寻找SO_ATTACH_BPF参数逻辑。在5.15.99的net/core/sock.c:1169行，找到了处理逻辑
排除关于bpf的操作（一些对prog程序的操作），跟进__sk_attach_prog。
在代码注释里的操作过后，成功将prog对象指向了sk->sk_filter->prog。
查找sk_filter代码，寻找调用函数。可以在很多函数中找到踪迹，在include/linux/filter.h中找到函数的原型。
sk_filter是封装好的sk->sk_filter调用原型，也有其他代码通过获取sk->sk_filter或者直接调用sk_filter_trim_cap来进行SOCKET_FILTER程序的运行。
跟进sk_filter_trim_cap函数，net/core/filter.c。
PF_MEMALLOC含义：
当前进程有很多可以释放的内存，如果能分配一点紧急内存给当前进程，那么当前进程可以返回更多的内存给系统。非内存管理子系统不应该使用这个标记，除非这次分配保证会释放更大的内存给系统。如果每个子系统都滥用这个标记，可能会耗尽内存管理子系统的保留内存。
程序首先检查 skb 是否设置了PF_MEMALLOC标志位，如果是的话，只有设置了 SOCK_MEMALLOC 标志的 socket 才能使用它，否则就返回 -ENOMEM 并增加统计计数器 LINUX_MIB_PFMEMALLOCDROP。这是为了防止内存不足的情况下，非紧急的 socket 占用有限的内存资源。
下一步，调用 BPF_CGROUP_RUN_PROG_INET_INGRESS() 函数，执行 cgroup 的 ingress hook上的 eBPF 程序，如果返回err，就return err。这是为了实现 cgroup 的网络隔离和限制功能。
这里如果开启了CGROUP_BPF的CGROUP_INET_INGRESS点，则调用__cgroup_bpf_run_filter_skb函数，执行CGROUP的filter程序。若没有开启，返回0值，继续执行代码。
cgroup细节之后讨论。
调用 security_sock_rcv_skb 函数，这是LSM的预留hook点，检查 socket 是否有权限接收 skb。
接下来，获取读锁，防止 sk_filter 被并发修改，从 sk 中获取 sk_filter 结构体指针。
取出sk->filter后，更新skb中的sock为当前传入socket，并且调用bpf_prog_run_save_cb执行bpf程序。然后把skb->sk赋值旧的socket回去。
如果返回的长度不为 0，就调用 pskb_trim 函数，将 skb 的数据部分裁剪到 cap 和返回的长度中的较大值，如果裁剪失败，就返回错误码；如果返回的长度为 0，就将错误码设置为 -EPERM，表示要丢弃 packet。
bpf prog执行的细节可以简单看一下。
其中涉及细节放到BPF系统源码分析里讲。
可以通过搜索sk->sk_filter、sk_filter、sk_filter_trim_cap，分析filter程序的调用
查找函数引用，回溯一下调用链。
查找调用sk_filter的函数，定位到sock_queue_rcv_skb(net/core/sock.c)（很多函数有注释，比如）
代码中的sk_filter就是埋点函数。
代码中有非常多的调用，很多都是各种协议的适配，比如J1939，搜索后发现是汽车的CAN总线通信协议。这里我们关注net/ieee802154/socket.c。
可以看到，dgram_rcv_skb(数据报SOCKET)和raw_rcv_skb都调用了sock_queue_rcv_skb。
ipv4的raw_rcv_skb逻辑也差不多，后面都进入同样的raw_rcv
跟进到net/ipv4/raw.c的 raw_rcv。
跟进raw_v4_input。这个函数主要做socket_raw的RX方向sk分配。SOCKET_RAW允许多个socket同时接收同一个数据包，
跟进到raw_local_deliver
跟进ip_local_deliver->ip_local_deliver_finish->ip_protocol_deliver_rcu->raw_local_deliver，这就来到了网络层转发到传输层的函数入口了。ip_local_deliver负责网络层转发到上层协议。由于SOCKET_RAW跳过传输层，因此检查设置在了这，具体细节可以看网络系统文章。
[Linux内核源码分析]网络子系统
net/ipv4/tcp_ipv4.c的tcp_filter函数调用了sk_filter_trim_cap
跟进到tcp_v4_rcv（AF_INET_tcp的recv函数）
在TCP_NEW_SYN_RECV的处理逻辑以及主体函数逻辑中，都有tcp_filter的函数调用
tcp_v4_rcv函数中会对TCP_NEW_SYN_RECV进行处理，如果连接检查成功，则需要新建控制块来处理连接，这个新建控制块的状态将会使用TCP_SYN_RECV状态；
搜索sk_filter找到了udp_queue_rcv_one_skb函数。这个函数位于udp_queue_rcv_skb内部
逆向一路向上跟进至udp_rcv，可知检测逻辑在UDP协议栈rcv处理函数内部。从udp_rcv顺序分析
跟进__udp4_lib_rcv
udp_unicast_rcv_skb和__udp4_lib_mcast_deliver都调用了udp_queue_rcv_skb，而udp_queue_rcv_skb内部包含udp_queue_rcv_one_skb。
最后在udp_queue_rcv_one_skb中调用了sk_filter_trim_cap。
调用链：udp_rcv->__udp4_lib_rcv->udp_unicast_rcv_skb/__udp4_lib_mcast_deliver->udp_queue_rcv_skb->udp_queue_rcv_one_skb->sk_filter_trim_cap
还有一些内核函数也调用sk_filter相关函数，但是属于通用sock处理逻辑（__sk_receive_skb），一些其他协议使用，比如DCCP、pppoe、l2tp等，这里就不加以分析。
跟踪点是__sk_destruct(net/core/sock.c)，其中会检查sock_filter是否还存在，还存在的话调用sk_filter_uncharge删除分配的内存。
跟进到sk_destruct
跟进__sk_free
跟进至sk_free
sk_free是内核删除socket对象的函数。内核通过sk_alloc分配socket对象。以下为tipc_sk_create(net/tipc/socket.c)的示例。通过sk_alloc创建socket对象，然后判断创建失败，sk_free释放内存。
处理逻辑调用链：sk_free->__sk_free->sk_destruct->__sk_destruct
net/packet/af_packet.c的run_filter会取出sk->sk_filter->prog程序，bpf执行
跟进到packet_rcv
跟进packet_create，这是PF_PACKET协议栈的create函数，其中创建了packet_sock，并且把packet_rcv指针赋值到协议栈处理函数中。当系统创建socket时，会调用inet_create，从inetsw数组中取出协议栈注册的函数，对应PF_PACKET的就是这里的packet_create。
packet_sock的结构
BPF_PROG_TYPE_SOCKET_FILTER类型的bpf程序，需要利用setsockopt函数绑定，埋点函数位于net/core/filter.c:sk_filter_trim_cap。
调用链总结
/* eBPF example program: * - creates arraymap in kernel with key 4 bytes and value 8 bytes
*
* - loads eBPF program:
* r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
* *(u32*)(fp - 4) = r0;
* // assuming packet is IPv4, lookup ip->proto in a map
* value = bpf_map_lookup_elem(map_fd, fp - 4);
* if (value)
* (*(u64*)value) += 1;
*
* - attaches this program to loopback interface "lo" raw socket
*
* - every second user space reads map[tcp], map[udp], map[icmp] to see
* how many packets of given protocol were seen on "lo"
*/
#include <stdio.h>#include <unistd.h>#include <assert.h>#include <linux/bpf.h>#include <string.h>#include <stdlib.h>#include <errno.h>#include <sys/socket.h>#include <arpa/inet.h>#include <linux/if_ether.h>#include <linux/ip.h>#include <stddef.h>#include <bpf/bpf.h>#include "bpf_insn.h"#include "sock_example.h"/* eBPF example program: * - creates arraymap in kernel with key 4 bytes and value 8 bytes
*
* - loads eBPF program:
* r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
* *(u32*)(fp - 4) = r0;
* // assuming packet is IPv4, lookup ip->proto in a map
* value = bpf_map_lookup_elem(map_fd, fp - 4);
* if (value)
* (*(u64*)value) += 1;
*
* - attaches this program to loopback interface "lo" raw socket
*
* - every second user space reads map[tcp], map[udp], map[icmp] to see
* how many packets of given protocol were seen on "lo"
*/
#include <stdio.h>#include <unistd.h>#include <assert.h>#include <linux/bpf.h>#include <string.h>#include <stdlib.h>#include <errno.h>#include <sys/socket.h>#include <arpa/inet.h>#include <linux/if_ether.h>#include <linux/ip.h>#include <stddef.h>#include <bpf/bpf.h>#include "bpf_insn.h"#include "sock_example.h"int sock = -1, map_fd, prog_fd, i, key;
long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value),
256, 0);
if (map_fd < 0) {
printf("failed to create map '%s'\n", strerror(errno));
goto cleanup;
}int sock = -1, map_fd, prog_fd, i, key;
long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value),
256, 0);
if (map_fd < 0) {
printf("failed to create map '%s'\n", strerror(errno));
goto cleanup;
}struct bpf_insn prog[] = {
BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol) /* R0 = ip->proto */),
BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
BPF_LD_MAP_FD(BPF_REG_1, map_fd),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
BPF_EXIT_INSN(),
};size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
struct bpf_insn prog[] = {
BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol) /* R0 = ip->proto */),
BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
BPF_LD_MAP_FD(BPF_REG_1, map_fd),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
BPF_EXIT_INSN(),
};size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
struct bpf_insn {
__u8 code; /* opcode */
__u8 dst_reg:4; /* dest register */
__u8 src_reg:4; /* source register */
__s16 off; /* signed offset */
__s32 imm; /* signed immediate constant */
};struct bpf_insn {
__u8 code; /* opcode */
__u8 dst_reg:4; /* dest register */
__u8 src_reg:4; /* source register */
__s16 off; /* signed offset */
__s32 imm; /* signed immediate constant */
};r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
*(u32*)(fp - 4) = r0;// assuming packet is IPv4, lookup ip->proto in a mapvalue = bpf_map_lookup_elem(map_fd, fp - 4);if (value)
(*(u64*)value) += 1;
r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
*(u32*)(fp - 4) = r0;// assuming packet is IPv4, lookup ip->proto in a mapvalue = bpf_map_lookup_elem(map_fd, fp - 4);if (value)
(*(u64*)value) += 1;
prog_fd = bpf_load_program(BPF_PROG_TYPE_SOCKET_FILTER, prog, insns_cnt, "GPL", 0, bpf_log_buf, BPF_LOG_BUF_SIZE);
if (prog_fd < 0) {
printf("failed to load prog '%s'\n", strerror(errno));
goto cleanup;
}prog_fd = bpf_load_program(BPF_PROG_TYPE_SOCKET_FILTER, prog, insns_cnt, "GPL", 0, bpf_log_buf, BPF_LOG_BUF_SIZE);
if (prog_fd < 0) {
printf("failed to load prog '%s'\n", strerror(errno));
goto cleanup;
}sock = open_raw_sock("lo");
if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
sizeof(prog_fd)) < 0) {
printf("setsockopt %s\n", strerror(errno));
goto cleanup;
}sock = open_raw_sock("lo");
if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
sizeof(prog_fd)) < 0) {
printf("setsockopt %s\n", strerror(errno));
goto cleanup;
}case SO_ATTACH_BPF:
ret = -EINVAL;
if (optlen == sizeof(u32)) {
u32 ufd;
ret = -EFAULT;
if (copy_from_sockptr(&ufd, optval, sizeof(ufd)))
break;
ret = sk_attach_bpf(ufd, sk);
}
break;
case SO_ATTACH_BPF:
ret = -EINVAL;
if (optlen == sizeof(u32)) {
u32 ufd;
ret = -EFAULT;
if (copy_from_sockptr(&ufd, optval, sizeof(ufd)))
break;
ret = sk_attach_bpf(ufd, sk);
}
break;
跳转到`sk_attach_bpf`函数（`net/core/filter.c:1571`）
跳转到`sk_attach_bpf`函数（`net/core/filter.c:1571`）
int sk_attach_bpf(u32 ufd, struct sock *sk)
{ struct bpf_prog *prog = __get_bpf(ufd, sk);
int err;
if (IS_ERR(prog))
return PTR_ERR(prog);
err = __sk_attach_prog(prog, sk);
if (err < 0) {
bpf_prog_put(prog);
return err;
}
return 0;
}int sk_attach_bpf(u32 ufd, struct sock *sk)
{ struct bpf_prog *prog = __get_bpf(ufd, sk);
int err;
if (IS_ERR(prog))
return PTR_ERR(prog);
err = __sk_attach_prog(prog, sk);
if (err < 0) {
bpf_prog_put(prog);
return err;
}
return 0;
}static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
{ //创建socket_filter的对象
// struct sk_filter {
// refcount_t refcnt;
// struct rcu_head rcu;
// struct bpf_prog *prog;
// };
struct sk_filter *fp, *old_fp;
fp = kmalloc(sizeof(*fp), GFP_KERNEL);
if (!fp)
return -ENOMEM;
fp->prog = prog;
// 为fp sk_filter对象分配一个socket的引用，如果失败，释放fp空间
if (!__sk_filter_charge(sk, fp)) {
kfree(fp);
return -ENOMEM;
}
refcount_set(&fp->refcnt, 1);
// 获取原先socket/filter过滤器
old_fp = rcu_dereference_protected(sk->sk_filter,
lockdep_sock_is_held(sk));
// 将sk->sk_filter的值变为我们新分配的fp
rcu_assign_pointer(sk->sk_filter, fp);
// 如果有淘汰下来的旧prog，需要对空间进行清理
if (old_fp)
sk_filter_uncharge(sk, old_fp);
return 0;
}static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
{ //创建socket_filter的对象
// struct sk_filter {
// refcount_t refcnt;
// struct rcu_head rcu;
// struct bpf_prog *prog;
// };
struct sk_filter *fp, *old_fp;
fp = kmalloc(sizeof(*fp), GFP_KERNEL);
if (!fp)
return -ENOMEM;
fp->prog = prog;
// 为fp sk_filter对象分配一个socket的引用，如果失败，释放fp空间
if (!__sk_filter_charge(sk, fp)) {
kfree(fp);
return -ENOMEM;
}
refcount_set(&fp->refcnt, 1);
// 获取原先socket/filter过滤器
old_fp = rcu_dereference_protected(sk->sk_filter,
lockdep_sock_is_held(sk));
// 将sk->sk_filter的值变为我们新分配的fp
rcu_assign_pointer(sk->sk_filter, fp);
// 如果有淘汰下来的旧prog，需要对空间进行清理
if (old_fp)
sk_filter_uncharge(sk, old_fp);
return 0;
}int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);
static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
{ return sk_filter_trim_cap(sk, skb, 1);
}int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);
static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
{ return sk_filter_trim_cap(sk, skb, 1);
}/ * sk_filter_trim_cap - run a packet through a socket filter
* @sk: sock associated with &sk_buff
* @skb: buffer to filter
* @cap: limit on how short the eBPF program may trim the packet
*
* Run the eBPF program and then cut skb->data to correct size returned by
* the program. If pkt_len is 0 we toss packet. If skb->len is smaller
* than pkt_len we keep whole skb->data. This is the socket level
* wrapper to bpf_prog_run. It returns 0 if the packet should
* be accepted or -EPERM if the packet should be tossed.
*
*/
int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)
{ int err;
struct sk_filter *filter;
/*
* If the skb was allocated from pfmemalloc reserves, only
* allow SOCK_MEMALLOC sockets to use it as this socket is
* helping free memory
*/
// 检查SKB是否分配PF_MEMALLOC标志位
if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC)) {
NET_INC_STATS(sock_net(sk), LINUX_MIB_PFMEMALLOCDROP);
return -ENOMEM;
}
err = BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb);
if (err)
return err;
//lsm框架hook点
err = security_sock_rcv_skb(sk, skb);
if (err)
return err;
rcu_read_lock();
filter = rcu_dereference(sk->sk_filter);
if (filter) {
struct sock *save_sk = skb->sk;
unsigned int pkt_len;
skb->sk = sk;
pkt_len = bpf_prog_run_save_cb(filter->prog, skb);
skb->sk = save_sk;
err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;
}
rcu_read_unlock();
return err;
}EXPORT_SYMBOL(sk_filter_trim_cap);/ * sk_filter_trim_cap - run a packet through a socket filter
* @sk: sock associated with &sk_buff
* @skb: buffer to filter
* @cap: limit on how short the eBPF program may trim the packet
*
* Run the eBPF program and then cut skb->data to correct size returned by
* the program. If pkt_len is 0 we toss packet. If skb->len is smaller
* than pkt_len we keep whole skb->data. This is the socket level
* wrapper to bpf_prog_run. It returns 0 if the packet should
* be accepted or -EPERM if the packet should be tossed.
*
*/
int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)
{ int err;
struct sk_filter *filter;
/*
* If the skb was allocated from pfmemalloc reserves, only
* allow SOCK_MEMALLOC sockets to use it as this socket is
* helping free memory
*/
// 检查SKB是否分配PF_MEMALLOC标志位
if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC)) {
NET_INC_STATS(sock_net(sk), LINUX_MIB_PFMEMALLOCDROP);
return -ENOMEM;
}
err = BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb);
if (err)
return err;
//lsm框架hook点
err = security_sock_rcv_skb(sk, skb);
if (err)
return err;
rcu_read_lock();
filter = rcu_dereference(sk->sk_filter);
if (filter) {
struct sock *save_sk = skb->sk;
unsigned int pkt_len;
skb->sk = sk;
pkt_len = bpf_prog_run_save_cb(filter->prog, skb);
skb->sk = save_sk;
err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;
}
rcu_read_unlock();
return err;
}EXPORT_SYMBOL(sk_filter_trim_cap);/* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb) \({ \ int __ret = 0; \
if (cgroup_bpf_enabled(CGROUP_INET_INGRESS)) \
__ret = __cgroup_bpf_run_filter_skb(sk, skb, \
CGROUP_INET_INGRESS); \
\
__ret; \
})/* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb) \({ \ int __ret = 0; \
if (cgroup_bpf_enabled(CGROUP_INET_INGRESS)) \
__ret = __cgroup_bpf_run_filter_skb(sk, skb, \
CGROUP_INET_INGRESS); \
\
__ret; \
})rcu_read_lock();filter = rcu_dereference(sk->sk_filter);if (filter) {
struct sock *save_sk = skb->sk;
unsigned int pkt_len;
skb->sk = sk;
pkt_len = bpf_prog_run_save_cb(filter->prog, skb);
skb->sk = save_sk;
err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;
}rcu_read_unlock();rcu_read_lock();filter = rcu_dereference(sk->sk_filter);if (filter) {
struct sock *save_sk = skb->sk;
unsigned int pkt_len;
skb->sk = sk;
pkt_len = bpf_prog_run_save_cb(filter->prog, skb);
skb->sk = save_sk;
err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;
}rcu_read_unlock();static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
struct sk_buff *skb)
{ u32 res;
migrate_disable();
res = __bpf_prog_run_save_cb(prog, skb);
migrate_enable();
return res;
}/* Must be invoked with migration disabled */static inline u32 __bpf_prog_run_save_cb(const struct bpf_prog *prog,
const void *ctx)
{ const struct sk_buff *skb = ctx;
u8 *cb_data = bpf_skb_cb(skb);
u8 cb_saved[BPF_SKB_CB_LEN];
u32 res;
if (unlikely(prog->cb_access)) {
memcpy(cb_saved, cb_data, sizeof(cb_saved));
memset(cb_data, 0, sizeof(cb_saved));
}
res = bpf_prog_run(prog, skb);
if (unlikely(prog->cb_access))
memcpy(cb_data, cb_saved, sizeof(cb_saved));
return res;
}static inline u8 *bpf_skb_cb(const struct sk_buff *skb)
{ /* eBPF programs may read/write skb->cb[] area to transfer meta
* data between tail calls. Since this also needs to work with
* tc, that scratch memory is mapped to qdisc_skb_cb's data area.
*
* In some socket filter cases, the cb unfortunately needs to be
* saved/restored so that protocol specific skb->cb[] data won't
* be lost. In any case, due to unpriviledged eBPF programs
* attached to sockets, we need to clear the bpf_skb_cb() area
* to not leak previous contents to user space.
*/
BUILD_BUG_ON(sizeof_field(struct __sk_buff, cb) != BPF_SKB_CB_LEN);
BUILD_BUG_ON(sizeof_field(struct __sk_buff, cb) !=
sizeof_field(struct qdisc_skb_cb, data));
return qdisc_skb_cb(skb)->data;
}static __always_inline u32 bpf_prog_run(const struct bpf_prog *prog, const void *ctx)
{ return __bpf_prog_run(prog, ctx, bpf_dispatcher_nop_func);
}static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog,
const void *ctx,
bpf_dispatcher_fn dfunc)
{ u32 ret;
cant_migrate();
if (static_branch_unlikely(&bpf_stats_enabled_key)) {
struct bpf_prog_stats *stats;
u64 start = sched_clock();
unsigned long flags;
ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
stats = this_cpu_ptr(prog->stats);
flags = u64_stats_update_begin_irqsave(&stats->syncp);
u64_stats_inc(&stats->cnt);
u64_stats_add(&stats->nsecs, sched_clock() - start);
u64_stats_update_end_irqrestore(&stats->syncp, flags);
} else {
ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
}
return ret;
}static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
struct sk_buff *skb)
{ u32 res;
migrate_disable();
res = __bpf_prog_run_save_cb(prog, skb);
migrate_enable();
return res;
}/* Must be invoked with migration disabled */static inline u32 __bpf_prog_run_save_cb(const struct bpf_prog *prog,
const void *ctx)
{ const struct sk_buff *skb = ctx;
u8 *cb_data = bpf_skb_cb(skb);
u8 cb_saved[BPF_SKB_CB_LEN];
u32 res;
if (unlikely(prog->cb_access)) {
memcpy(cb_saved, cb_data, sizeof(cb_saved));
memset(cb_data, 0, sizeof(cb_saved));
}
res = bpf_prog_run(prog, skb);
if (unlikely(prog->cb_access))
memcpy(cb_data, cb_saved, sizeof(cb_saved));
return res;
}static inline u8 *bpf_skb_cb(const struct sk_buff *skb)
{ /* eBPF programs may read/write skb->cb[] area to transfer meta
* data between tail calls. Since this also needs to work with
* tc, that scratch memory is mapped to qdisc_skb_cb's data area.
*
* In some socket filter cases, the cb unfortunately needs to be
* saved/restored so that protocol specific skb->cb[] data won't
* be lost. In any case, due to unpriviledged eBPF programs
* attached to sockets, we need to clear the bpf_skb_cb() area
* to not leak previous contents to user space.
*/
BUILD_BUG_ON(sizeof_field(struct __sk_buff, cb) != BPF_SKB_CB_LEN);
BUILD_BUG_ON(sizeof_field(struct __sk_buff, cb) !=
sizeof_field(struct qdisc_skb_cb, data));
return qdisc_skb_cb(skb)->data;
}static __always_inline u32 bpf_prog_run(const struct bpf_prog *prog, const void *ctx)
{ return __bpf_prog_run(prog, ctx, bpf_dispatcher_nop_func);
}static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog,
const void *ctx,
bpf_dispatcher_fn dfunc)
{ u32 ret;
cant_migrate();
if (static_branch_unlikely(&bpf_stats_enabled_key)) {
struct bpf_prog_stats *stats;
u64 start = sched_clock();
unsigned long flags;
ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
stats = this_cpu_ptr(prog->stats);
flags = u64_stats_update_begin_irqsave(&stats->syncp);
u64_stats_inc(&stats->cnt);
u64_stats_add(&stats->nsecs, sched_clock() - start);
u64_stats_update_end_irqrestore(&stats->syncp, flags);
} else {
ret = dfunc(ctx, prog->insnsi, prog->bpf_func);
}
return ret;
}int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{ int err;
err = sk_filter(sk, skb);
if (err)
return err;
return __sock_queue_rcv_skb(sk, skb);
}EXPORT_SYMBOL(sock_queue_rcv_skb);int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{ int err;
err = sk_filter(sk, skb);
if (err)
return err;
return __sock_queue_rcv_skb(sk, skb);
}EXPORT_SYMBOL(sock_queue_rcv_skb);static int raw_rcv_skb(struct sock *sk, struct sk_buff *skb)
{ skb = skb_share_check(skb, GFP_ATOMIC);
if (!skb)
return NET_RX_DROP;
if (sock_queue_rcv_skb(sk, skb) < 0) {
kfree_skb(skb);
return NET_RX_DROP;
}
return NET_RX_SUCCESS;
}static int raw_rcv_skb(struct sock *sk, struct sk_buff *skb)
{ skb = skb_share_check(skb, GFP_ATOMIC);
if (!skb)
return NET_RX_DROP;
if (sock_queue_rcv_skb(sk, skb) < 0) {
kfree_skb(skb);
return NET_RX_DROP;
}
return NET_RX_SUCCESS;
}static int raw_rcv_skb(struct sock *sk, struct sk_buff *skb)
{ /* Charge it to the socket. */
ipv4_pktinfo_prepare(sk, skb);
if (sock_queue_rcv_skb(sk, skb) < 0) {
kfree_skb(skb);
return NET_RX_DROP;
}
return NET_RX_SUCCESS;
}static int raw_rcv_skb(struct sock *sk, struct sk_buff *skb)
{ /* Charge it to the socket. */
ipv4_pktinfo_prepare(sk, skb);
if (sock_queue_rcv_skb(sk, skb) < 0) {
kfree_skb(skb);
return NET_RX_DROP;
}
return NET_RX_SUCCESS;
}int raw_rcv(struct sock *sk, struct sk_buff *skb)
{ // 安全策略检查
if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) {
atomic_inc(&sk->sk_drops);
kfree_skb(skb);
return NET_RX_DROP;
}
//NFHOOK埋点，重置跟踪信息
nf_reset_ct(skb);
skb_push(skb, skb->data - skb_network_header(skb));
raw_rcv_skb(sk, skb);
return 0;
}int raw_rcv(struct sock *sk, struct sk_buff *skb)
{ // 安全策略检查
if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) {
atomic_inc(&sk->sk_drops);
kfree_skb(skb);
return NET_RX_DROP;
}
//NFHOOK埋点，重置跟踪信息
nf_reset_ct(skb);
skb_push(skb, skb->data - skb_network_header(skb));
raw_rcv_skb(sk, skb);
return 0;
}/* IP input processing comes here for RAW socket delivery. * Caller owns SKB, so we must make clones.
*
* RFC 1122: SHOULD pass TOS value up to the transport layer.
* -> It does. And not only TOS, but all IP header.
*/
static int raw_v4_input(struct sk_buff *skb, const struct iphdr *iph, int hash)
{ ......
// 根据网络设备寻找匹配的socket
net = dev_net(skb->dev);
sk = __raw_v4_lookup(net, __sk_head(head), iph->protocol,
iph->saddr, iph->daddr, dif, sdif);
while (sk) {
delivered = 1;
if ((iph->protocol != IPPROTO_ICMP || !icmp_filter(sk, skb)) &&
ip_mc_sf_allow(sk, iph->daddr, iph->saddr,
skb->dev->ifindex, sdif)) {
// clone的目的是不共享数据包，socket拥有自己的数据包
struct sk_buff *clone = skb_clone(skb, GFP_ATOMIC);
/* Not releasing hash table! */
if (clone)
raw_rcv(sk, clone);
}
sk = __raw_v4_lookup(net, sk_next(sk), iph->protocol,
iph->saddr, iph->daddr,
dif, sdif);
}
out: read_unlock(&raw_v4_hashinfo.lock);
return delivered;
}/* IP input processing comes here for RAW socket delivery. * Caller owns SKB, so we must make clones.
*
* RFC 1122: SHOULD pass TOS value up to the transport layer.
* -> It does. And not only TOS, but all IP header.
*/
static int raw_v4_input(struct sk_buff *skb, const struct iphdr *iph, int hash)
{ ......
// 根据网络设备寻找匹配的socket
net = dev_net(skb->dev);
sk = __raw_v4_lookup(net, __sk_head(head), iph->protocol,
iph->saddr, iph->daddr, dif, sdif);
while (sk) {
delivered = 1;
if ((iph->protocol != IPPROTO_ICMP || !icmp_filter(sk, skb)) &&
ip_mc_sf_allow(sk, iph->daddr, iph->saddr,
skb->dev->ifindex, sdif)) {
// clone的目的是不共享数据包，socket拥有自己的数据包
struct sk_buff *clone = skb_clone(skb, GFP_ATOMIC);
/* Not releasing hash table! */
if (clone)
raw_rcv(sk, clone);
}
sk = __raw_v4_lookup(net, sk_next(sk), iph->protocol,
iph->saddr, iph->daddr,
[招生]科锐逆向工程师培训(2024年11月15日实地，远程教学同时开班, 第51期)
最后于 2024-5-11 18:55
被天堂猪0ink编辑
，原因： 编辑样式
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