Introduce IPv6-enabled version of get_client_address. The legacy mount

[nfs-utils.git] / utils / mount / network.c

diff --git a/utils/mount/network.c b/utils/mount/network.c
index 3f2721b802450134acd165b673f059615cc6f35f..849ce1d6825da3ad0d8865b28876a54d5713a91f 100644 (file)
--- a/utils/mount/network.c
+++ b/utils/mount/network.c
@@ -918,3 +918,121 @@ int get_client_address(struct sockaddr_in *saddr, struct sockaddr_in *caddr)
        }
        return 1;
 }
        }
        return 1;
 }

+
+/*
+ * Try a getsockname() on a connected datagram socket.
+ *
+ * Returns 1 and fills in @buf if successful; otherwise, zero.
+ *
+ * A connected datagram socket prevents leaving a socket in TIME_WAIT.
+ * This conserves the ephemeral port number space, helping reduce failed
+ * socket binds during mount storms.
+ */
+static int nfs_ca_sockname(const struct sockaddr *sap, const socklen_t salen,
+                          struct sockaddr *buf, socklen_t *buflen)
+{
+       struct sockaddr_in sin = {
+               .sin_family             = AF_INET,
+               .sin_addr.s_addr        = htonl(INADDR_ANY),
+       };
+       struct sockaddr_in6 sin6 = {
+               .sin6_family            = AF_INET6,
+               .sin6_addr              = IN6ADDR_ANY_INIT,
+       };
+       int sock;
+
+       sock = socket(sap->sa_family, SOCK_DGRAM, IPPROTO_UDP);
+       if (sock < 0)
+               return 0;
+
+       switch (sap->sa_family) {
+       case AF_INET:
+               if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
+                       close(sock);
+                       return 0;
+               }
+               break;
+       case AF_INET6:
+               if (bind(sock, (struct sockaddr *)&sin6, sizeof(sin6)) < 0) {
+                       close(sock);
+                       return 0;
+               }
+               break;
+       default:
+               errno = EAFNOSUPPORT;
+               return 0;
+       }
+
+       if (connect(sock, sap, salen) < 0) {
+               close(sock);
+               return 0;
+       }
+
+       return !getsockname(sock, buf, buflen);
+}
+
+/*
+ * Try to generate an address that prevents the server from calling us.
+ *
+ * Returns 1 and fills in @buf if successful; otherwise, zero.
+ */
+static int nfs_ca_gai(const struct sockaddr *sap, const socklen_t salen,
+                     struct sockaddr *buf, socklen_t *buflen)
+{
+       struct addrinfo *gai_results;
+       struct addrinfo gai_hint = {
+               .ai_family      = sap->sa_family,
+               .ai_flags       = AI_PASSIVE,   /* ANYADDR */
+       };
+
+       if (getaddrinfo(NULL, "", &gai_hint, &gai_results))
+               return 0;
+
+       *buflen = gai_results->ai_addrlen;
+       memcpy(buf, gai_results->ai_addr, *buflen);
+
+       freeaddrinfo(gai_results);
+
+       return 1;
+}
+
+/**
+ * nfs_callback_address - acquire our local network address
+ * @sap: pointer to address of remote
+ * @sap_len: length of address
+ * @buf: pointer to buffer to be filled in with local network address
+ * @buflen: IN: length of buffer to fill in; OUT: length of filled-in address
+ *
+ * Discover a network address that an NFSv4 server can use to call us back.
+ * On multi-homed clients, this address depends on which NIC we use to
+ * route requests to the server.
+ *
+ * Returns 1 and fills in @buf if an unambiguous local address is
+ * available; returns 1 and fills in an appropriate ANYADDR address
+ * if a local address isn't available; otherwise, returns zero.
+ */
+int nfs_callback_address(const struct sockaddr *sap, const socklen_t salen,
+                        struct sockaddr *buf, socklen_t *buflen)
+{
+       struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)buf;
+
+       if (nfs_ca_sockname(sap, salen, buf, buflen) == 0)
+               if (nfs_ca_gai(sap, salen, buf, buflen) == 0)
+                       goto out_failed;
+
+       /*
+        * The server can't use an interface ID that was generated
+        * here on the client, so always clear sin6_scope_id.
+        */
+       if (sin6->sin6_family == AF_INET6)
+               sin6->sin6_scope_id = 0;
+
+       return 1;
+
+out_failed:
+       *buflen = 0;
+       if (verbose)
+               nfs_error(_("%s: failed to construct callback address"));
+       return 0;
+
+}