3 files changed, 18 insertions, 1 deletions
diff --git a/src/core/bpf-socket-bind.c b/src/core/bpf-socket-bind.c
index 9f290ab..88ab487 100644
--- a/src/core/bpf-socket-bind.c
+++ b/src/core/bpf-socket-bind.c
@@ -32,6 +32,15 @@ static int update_rules_map(
 
         assert(map_fd >= 0);
 
+        if (!head) {
+                static const struct socket_bind_rule val = {
+                        .address_family = SOCKET_BIND_RULE_AF_MATCH_NOTHING,
+                };
+
+                if (sym_bpf_map_update_elem(map_fd, &i, &val, BPF_ANY) != 0)
+                        return -errno;
+        }
+
         LIST_FOREACH(socket_bind_items, item, head) {
                 struct socket_bind_rule val = {
                         .address_family = (uint32_t) item->address_family,
diff --git a/src/core/bpf/socket_bind/socket-bind-api.bpf.h b/src/core/bpf/socket_bind/socket-bind-api.bpf.h
index 277b9bb..4fe08f1 100644
--- a/src/core/bpf/socket_bind/socket-bind-api.bpf.h
+++ b/src/core/bpf/socket_bind/socket-bind-api.bpf.h
@@ -7,13 +7,17 @@
  */
 
 #include <linux/types.h>
+#include <stdint.h>
 
 /*
  * Bind rule is matched with socket fields accessible to cgroup/bind{4,6} hook
  * through bpf_sock_addr struct.
- * 'address_family' is expected to be one of AF_UNSPEC, AF_INET or AF_INET6.
+ * 'address_family' is expected to be one of AF_UNSPEC, AF_INET, AF_INET6 or the
+ * magic SOCKET_BIND_RULE_AF_MATCH_NOTHING.
  * Matching by family is bypassed for rules with AF_UNSPEC set, which makes the
  * rest of a rule applicable for both IPv4 and IPv6 addresses.
+ * If SOCKET_BIND_RULE_AF_MATCH_NOTHING is set the rule fails unconditionally
+ * and other checks are skipped.
  * If matching by family is either successful or bypassed, a rule and a socket
  * are matched by ip protocol.
  * If 'protocol' is 0, matching is bypassed.
@@ -49,3 +53,4 @@ struct socket_bind_rule {
 };
 
 #define SOCKET_BIND_MAX_RULES 128
+#define SOCKET_BIND_RULE_AF_MATCH_NOTHING UINT32_MAX
diff --git a/src/core/bpf/socket_bind/socket-bind.bpf.c b/src/core/bpf/socket_bind/socket-bind.bpf.c
index b7972a8..da9f9d1 100644
--- a/src/core/bpf/socket_bind/socket-bind.bpf.c
+++ b/src/core/bpf/socket_bind/socket-bind.bpf.c
@@ -55,6 +55,9 @@ static __always_inline bool match(
                 __u32 protocol,
                 __u16 port,
                 const struct socket_bind_rule *r) {
+        if (r->address_family == SOCKET_BIND_RULE_AF_MATCH_NOTHING)
+                return false;
+
         return match_af(address_family, r) &&
                 match_protocol(protocol, r) &&
                 match_user_port(port, r);