Re: [PATCH net-next v3 3/3] A Sample of using socket cookie and uid for traffic monitoring

+/* This test is a demo of using get_socket_uid and get_socket_cookie
+ * helper function to do per socket based network traffic monitoring.
+ * It requires iptable version higher then 1.6.1. to load pined eBPF
+ * program into the xt_bpf match.

iptable -> iptables (everywhre
pined -> pinned

+ * Clean up: if using shell script, the script file will delete the iptables
+ * rule and unmount the bpf program when exit. Else the iptables rule need
+ * to be deleted using:
+ *   iptables -D INPUT -m bpf --object-pinned ${mnt_dir}/bpf_prog -j ACCEPT

this is already in the wrapper script

+       struct bpf_insn prog[] = {
+               /*
+                * it for future usage. value stored in R6 to R10 will not be
+                * reset after a bpf helper function call.

garbled comment

+                */
+               BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+               /*
+                * pc1: BPF_FUNC_get_socket_cookie takes one parameter,
+                * R1: sk_buff
+                */
+               BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+                               BPF_FUNC_get_socket_cookie),
+               /* pc2-4: save &socketCookie to r7 for future usage*/
+               BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
+               BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+               BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -8),
+               /*
+                * pc5-8: set up the registers for BPF_FUNC_map_lookup_elem,
+                * it takes two parameters (R1: map_fd,  R2: &socket_cookie)
+                */
+               BPF_LD_MAP_FD(BPF_REG_1, map_fd),
+               BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+               BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+                               BPF_FUNC_map_lookup_elem),
+               /*
+                * pc9. if r0 != 0x0, go to pc+14, since we have the cookie
+                * stored already
+                * Otherwise do pc10-22 to setup a new data entry.
+                */
+               BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 14),
+               BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+               BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+                               BPF_FUNC_get_socket_uid),
+               /*
+                * Place a struct stats in the R10 stack and sequentially
+                * place the member value into the memory. Packets value
+                * is set by directly place a IMM value 1 into the stack.
+                */
+               BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0,
+                               -32 + offsetof(struct stats, uid)),
+               BPF_ST_MEM(BPF_DW, BPF_REG_10,
+                               -32 + offsetof(struct stats, packets), 1),
+               /*
+                * __sk_buff is a special struct used for eBPF program to
+                * directly access some sk_buff field.
+                */
+               BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6,
+                               offsetof(struct __sk_buff, len)),
+               BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_1,
+                               -32 + offsetof(struct stats, bytes)),
+               /*
+                * add new map entry using BPF_FUNC_map_update_elem, it takes
+                * 4 parameters (R1: map_fd, R2: &socket_cookie, R3: &stats)

R4: flags

+                */
+               BPF_LD_MAP_FD(BPF_REG_1, map_fd),
+               BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+               BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
+               BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -32),
+               BPF_MOV64_IMM(BPF_REG_4, 0),
+               BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+                               BPF_FUNC_map_update_elem),
+               BPF_JMP_IMM(BPF_JA, 0, 0, 5),
+               /*
+                * pc24-30 update the packet info to a exist data entry, it can
+                * be done by directly write to pointers instead of using
+                * BPF_FUNC_map_update_elem helper function
+                */
+               BPF_MOV64_REG(BPF_REG_9, BPF_REG_0),
+               BPF_MOV64_IMM(BPF_REG_1, 1),
+               BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_9, BPF_REG_1,
+                               offsetof(struct stats, packets), 0),

BPF_STX_XADD here and below

+               BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6,
+                               offsetof(struct __sk_buff, len)),
+               BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_9, BPF_REG_1,
+                                         offsetof(struct stats, bytes), 0),
+               BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_6,
+                               offsetof(struct __sk_buff, len)),

No requirement to return len. It goes unused, can just return non-zero
immediate.

+static void prog_attach_iptables(char *file)
+{
+       int ret;
+       char rules[100];
+
+       if (bpf_obj_pin(prog_fd, file))
+               error(1, errno, "bpf_obj_pin");
+       sprintf(rules, "iptables -A INPUT -m bpf --object-pinned %s -j ACCEPT",
+               file);

this is a test, but still: unsafe to pass user input unchecked to sprintf

+                       printf("cookie: %u, uid: 0x%x, Pakcet Count: %lu,"

Packet

Don't modify state outside the test environment. Perhaps use a temporary dir:

mnt_dir=$(mktemp -d --tmp)

and remove it in on_exit