inet_diag: add support for cgroup filter

This patch adds ability to filter sockets based on cgroup v2 ID.
Such filter is helpful in ss utility for filtering sockets by
cgroup pathname.

Signed-off-by: Dmitry Yakunin <zeil@yandex-team.ru>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/inet_diag.h

@@ -96,6 +96,7 @@ enum {
 	INET_DIAG_BC_MARK_COND,
 	INET_DIAG_BC_S_EQ,
 	INET_DIAG_BC_D_EQ,
+	INET_DIAG_BC_CGROUP_COND,   /* u64 cgroup v2 ID */
 };
 
 struct inet_diag_hostcond {

net/ipv4/inet_diag.c

@@ -43,6 +43,9 @@ struct inet_diag_entry {
 	u16 userlocks;
 	u32 ifindex;
 	u32 mark;
+#ifdef CONFIG_SOCK_CGROUP_DATA
+	u64 cgroup_id;
+#endif
 };
 
 static DEFINE_MUTEX(inet_diag_table_mutex);
@@ -682,6 +685,16 @@ static int inet_diag_bc_run(const struct nlattr *_bc,
 				yes = 0;
 			break;
 		}
+#ifdef CONFIG_SOCK_CGROUP_DATA
+		case INET_DIAG_BC_CGROUP_COND: {
+			u64 cgroup_id;
+
+			cgroup_id = get_unaligned((const u64 *)(op + 1));
+			if (cgroup_id != entry->cgroup_id)
+				yes = 0;
+			break;
+		}
+#endif
 		}
 
 		if (yes) {
@@ -732,6 +745,9 @@ int inet_diag_bc_sk(const struct nlattr *bc, struct sock *sk)
 		entry.mark = inet_rsk(inet_reqsk(sk))->ir_mark;
 	else
 		entry.mark = 0;
+#ifdef CONFIG_SOCK_CGROUP_DATA
+	entry.cgroup_id = cgroup_id(sock_cgroup_ptr(&sk->sk_cgrp_data));
+#endif
 
 	return inet_diag_bc_run(bc, &entry);
 }
@@ -821,6 +837,15 @@ static bool valid_markcond(const struct inet_diag_bc_op *op, int len,
 	return len >= *min_len;
 }
 
+#ifdef CONFIG_SOCK_CGROUP_DATA
+static bool valid_cgroupcond(const struct inet_diag_bc_op *op, int len,
+			     int *min_len)
+{
+	*min_len += sizeof(u64);
+	return len >= *min_len;
+}
+#endif
+
 static int inet_diag_bc_audit(const struct nlattr *attr,
 			      const struct sk_buff *skb)
 {
@@ -863,6 +888,12 @@ static int inet_diag_bc_audit(const struct nlattr *attr,
 			if (!valid_markcond(bc, len, &min_len))
 				return -EINVAL;
 			break;
+#ifdef CONFIG_SOCK_CGROUP_DATA
+		case INET_DIAG_BC_CGROUP_COND:
+			if (!valid_cgroupcond(bc, len, &min_len))
+				return -EINVAL;
+			break;
+#endif
 		case INET_DIAG_BC_AUTO:
 		case INET_DIAG_BC_JMP:
 		case INET_DIAG_BC_NOP: