tcp: ulp: add functions to dump ulp-specific information

currently, only getsockopt(TCP_ULP) can be invoked to know if a ULP is on
top of a TCP socket. Extend idiag_get_aux() and idiag_get_aux_size(),
introduced by commit b37e88407c1d ("inet_diag: allow protocols to provide
additional data"), to report the ULP name and other information that can
be made available by the ULP through optional functions.

Users having CAP_NET_ADMIN privileges will then be able to retrieve this
information through inet_diag_handler, if they specify INET_DIAG_INFO in
the request.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 62 insertions, 1 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 77fe87f7a992..c9a3f9688223 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2122,6 +2122,9 @@ struct tcp_ulp_ops {
         void (*update)(struct sock *sk, struct proto *p);
         /* cleanup ulp */
         void (*release)(struct sock *sk);
+        /* diagnostic */
+        int (*get_info)(const struct sock *sk, struct sk_buff *skb);
+        size_t (*get_info_size)(const struct sock *sk);
 
         char            name[TCP_ULP_NAME_MAX];
         struct module   *owner;
diff --git a/include/uapi/linux/inet_diag.h b/include/uapi/linux/inet_diag.h
index e8baca85bac6..e2c6273274f3 100644
--- a/include/uapi/linux/inet_diag.h
+++ b/include/uapi/linux/inet_diag.h
@@ -153,11 +153,19 @@ enum {
         INET_DIAG_BBRINFO,      /* request as INET_DIAG_VEGASINFO */
         INET_DIAG_CLASS_ID,     /* request as INET_DIAG_TCLASS */
         INET_DIAG_MD5SIG,
+        INET_DIAG_ULP_INFO,
         __INET_DIAG_MAX,
 };
 
 #define INET_DIAG_MAX (__INET_DIAG_MAX - 1)
 
+enum {
+        INET_ULP_INFO_UNSPEC,
+        INET_ULP_INFO_NAME,
+        __INET_ULP_INFO_MAX,
+};
+#define INET_ULP_INFO_MAX (__INET_ULP_INFO_MAX - 1)
+
 /* INET_DIAG_MEM */
 
 struct inet_diag_meminfo {
diff --git a/net/ipv4/tcp_diag.c b/net/ipv4/tcp_diag.c
index a3a386236d93..babc156deabb 100644
--- a/net/ipv4/tcp_diag.c
+++ b/net/ipv4/tcp_diag.c
@@ -81,13 +81,42 @@ static int tcp_diag_put_md5sig(struct sk_buff *skb,
 }
 #endif
 
+static int tcp_diag_put_ulp(struct sk_buff *skb, struct sock *sk,
+                            const struct tcp_ulp_ops *ulp_ops)
+{
+        struct nlattr *nest;
+        int err;
+
+        nest = nla_nest_start_noflag(skb, INET_DIAG_ULP_INFO);
+        if (!nest)
+                return -EMSGSIZE;
+
+        err = nla_put_string(skb, INET_ULP_INFO_NAME, ulp_ops->name);
+        if (err)
+                goto nla_failure;
+
+        if (ulp_ops->get_info)
+                err = ulp_ops->get_info(sk, skb);
+        if (err)
+                goto nla_failure;
+
+        nla_nest_end(skb, nest);
+        return 0;
+
+nla_failure:
+        nla_nest_cancel(skb, nest);
+        return err;
+}
+
 static int tcp_diag_get_aux(struct sock *sk, bool net_admin,
                             struct sk_buff *skb)
 {
+        struct inet_connection_sock *icsk = inet_csk(sk);
+        int err = 0;
+
 #ifdef CONFIG_TCP_MD5SIG
         if (net_admin) {
                 struct tcp_md5sig_info *md5sig;
-                int err = 0;
 
                 rcu_read_lock();
                 md5sig = rcu_dereference(tcp_sk(sk)->md5sig_info);
@@ -99,11 +128,21 @@ static int tcp_diag_get_aux(struct sock *sk, bool net_admin,
         }
 #endif
 
+        if (net_admin) {
+                const struct tcp_ulp_ops *ulp_ops;
+
+                ulp_ops = icsk->icsk_ulp_ops;
+                if (ulp_ops)
+                        err = tcp_diag_put_ulp(skb, sk, ulp_ops);
+                if (err)
+                        return err;
+        }
         return 0;
 }
 
 static size_t tcp_diag_get_aux_size(struct sock *sk, bool net_admin)
 {
+        struct inet_connection_sock *icsk = inet_csk(sk);
         size_t size = 0;
 
 #ifdef CONFIG_TCP_MD5SIG
@@ -124,6 +163,17 @@ static size_t tcp_diag_get_aux_size(struct sock *sk, bool net_admin)
         }
 #endif
 
+        if (net_admin) {
+                const struct tcp_ulp_ops *ulp_ops;
+
+                ulp_ops = icsk->icsk_ulp_ops;
+                if (ulp_ops) {
+                        size += nla_total_size(0) +
+                                nla_total_size(TCP_ULP_NAME_MAX);
+                        if (ulp_ops->get_info_size)
+                                size += ulp_ops->get_info_size(sk);
+                }
+        }
         return size;
 }