xdp: use BPF_MAP_TYPE_HASH for the filter map (#898)

BPF_MAP_TYPE_ARRAY size is limited cause udp4_dp_filter_fd update
fail(-7), eBPF map use locked memory.

Signed-off-by: Frank Du <[email protected]>
(cherry picked from commit 002b38e)

Author: frankdjx

manager/mtl.xdp.c

@@ -13,10 +13,10 @@
 char LICENSE[] SEC("license") = "Dual BSD/GPL";
 
 struct {
-  __uint(type, BPF_MAP_TYPE_ARRAY);
-  __uint(max_entries, 65536);
-  __type(key, int);
-  __type(value, int);
+  __uint(type, BPF_MAP_TYPE_HASH);
+  __uint(max_entries, 256); /* max 256 filters */
+  __type(key, __u16);       /* udp port: 16bit */
+  __type(value, __u8);      /* only 1 or 0 */
 } udp4_dp_filter SEC(".maps");
 
 struct {
@@ -25,8 +25,8 @@ struct {
   __uint(XDP_DROP, 1);
 } XDP_RUN_CONFIG(mtl_dp_filter);
 
-static int __always_inline lookup_udp4_dp(int dp) {
-  int* value;
+static int __always_inline lookup_udp4_dp(__u16 dp) {
+  __u8* value;
 
   value = bpf_map_lookup_elem(&udp4_dp_filter, &dp);
   if (value && *value != 0) return 1;
@@ -56,7 +56,7 @@ int mtl_dp_filter(struct xdp_md* ctx) {
   ret = parse_udphdr(&nh, data_end, &udphdr);
   if (ret < 0) return XDP_PASS;
 
-  int dst_port = bpf_ntohs(udphdr->dest);
+  __u16 dst_port = bpf_ntohs(udphdr->dest);
   if (lookup_udp4_dp(dst_port) == 0) return XDP_PASS;
 
   /* go to next program: xsk_def_prog */

manager/mtl_interface.hpp

@@ -119,10 +119,12 @@ int mtl_interface::update_udp_dp_filter(uint16_t dst_port, bool add) {
     return 0;
   }
 
-  int value = add ? 1 : 0;
-  if (bpf_map_update_elem(udp4_dp_filter_fd, &dst_port, &value, BPF_ANY) < 0) {
+  uint8_t value = add ? 1 : 0;
+  int ret = bpf_map_update_elem(udp4_dp_filter_fd, &dst_port, &value, BPF_ANY);
+  if (ret < 0) {
     log(log_level::ERROR,
-        "Failed to update udp4_dp_filter map, dst_port: " + std::to_string(dst_port));
+        "Failed to update udp4_dp_filter map, dst_port: " + std::to_string(dst_port) +
+            ", error: " + std::to_string(ret));
     return -1;
   }
 
@@ -440,7 +442,8 @@ int mtl_interface::load_xdp() {
     return -1;
   }
 
-  log(log_level::INFO, "Loaded xdp prog.");
+  log(log_level::INFO,
+      "Loaded xdp prog succ, udp4_dp_filter_fd: " + std::to_string(udp4_dp_filter_fd));
   return 0;
 }