sctp: add support for SCTP_DSTADDRV4/6 Information for sendmsg

This patch is to add support for Destination IPv4/6 Address options
for sendmsg, as described in section 5.3.9/10 of RFC6458.

With this option, you can provide more than one destination addrs
to sendmsg when creating asoc, like sctp_connectx.

It's also a necessary send info for sctp_sendv.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -2113,6 +2113,7 @@ struct sctp_cmsgs {
 	struct sctp_sndrcvinfo *srinfo;
 	struct sctp_sndinfo *sinfo;
 	struct sctp_prinfo *prinfo;
+	struct msghdr *addrs_msg;
 };
 
 /* Structure for tracking memory objects */

include/uapi/linux/sctp.h

@@ -308,6 +308,12 @@ typedef enum sctp_cmsg_type {
 #define SCTP_NXTINFO	SCTP_NXTINFO
 	SCTP_PRINFO,		/* 5.3.7 SCTP PR-SCTP Information Structure */
 #define SCTP_PRINFO	SCTP_PRINFO
+	SCTP_AUTHINFO,		/* 5.3.8 SCTP AUTH Information Structure (RESERVED) */
+#define SCTP_AUTHINFO	SCTP_AUTHINFO
+	SCTP_DSTADDRV4,		/* 5.3.9 SCTP Destination IPv4 Address Structure */
+#define SCTP_DSTADDRV4	SCTP_DSTADDRV4
+	SCTP_DSTADDRV6,		/* 5.3.10 SCTP Destination IPv6 Address Structure */
+#define SCTP_DSTADDRV6	SCTP_DSTADDRV6
 } sctp_cmsg_t;
 
 /*

net/sctp/socket.c

@@ -1676,6 +1676,7 @@ static int sctp_sendmsg_new_asoc(struct sock *sk, __u16 sflags,
 	struct net *net = sock_net(sk);
 	struct sctp_association *asoc;
 	enum sctp_scope scope;
+	struct cmsghdr *cmsg;
 	int err = -EINVAL;
 
 	*tp = NULL;
@@ -1741,6 +1742,67 @@ static int sctp_sendmsg_new_asoc(struct sock *sk, __u16 sflags,
 		goto free;
 	}
 
+	if (!cmsgs->addrs_msg)
+		return 0;
+
+	/* sendv addr list parse */
+	for_each_cmsghdr(cmsg, cmsgs->addrs_msg) {
+		struct sctp_transport *transport;
+		struct sctp_association *old;
+		union sctp_addr _daddr;
+		int dlen;
+
+		if (cmsg->cmsg_level != IPPROTO_SCTP ||
+		    (cmsg->cmsg_type != SCTP_DSTADDRV4 &&
+		     cmsg->cmsg_type != SCTP_DSTADDRV6))
+			continue;
+
+		daddr = &_daddr;
+		memset(daddr, 0, sizeof(*daddr));
+		dlen = cmsg->cmsg_len - sizeof(struct cmsghdr);
+		if (cmsg->cmsg_type == SCTP_DSTADDRV4) {
+			if (dlen < sizeof(struct in_addr))
+				goto free;
+
+			dlen = sizeof(struct in_addr);
+			daddr->v4.sin_family = AF_INET;
+			daddr->v4.sin_port = htons(asoc->peer.port);
+			memcpy(&daddr->v4.sin_addr, CMSG_DATA(cmsg), dlen);
+		} else {
+			if (dlen < sizeof(struct in6_addr))
+				goto free;
+
+			dlen = sizeof(struct in6_addr);
+			daddr->v6.sin6_family = AF_INET6;
+			daddr->v6.sin6_port = htons(asoc->peer.port);
+			memcpy(&daddr->v6.sin6_addr, CMSG_DATA(cmsg), dlen);
+		}
+		err = sctp_verify_addr(sk, daddr, sizeof(*daddr));
+		if (err)
+			goto free;
+
+		old = sctp_endpoint_lookup_assoc(ep, daddr, &transport);
+		if (old && old != asoc) {
+			if (old->state >= SCTP_STATE_ESTABLISHED)
+				err = -EISCONN;
+			else
+				err = -EALREADY;
+			goto free;
+		}
+
+		if (sctp_endpoint_is_peeled_off(ep, daddr)) {
+			err = -EADDRNOTAVAIL;
+			goto free;
+		}
+
+		transport = sctp_assoc_add_peer(asoc, daddr, GFP_KERNEL,
+						SCTP_UNKNOWN);
+		if (!transport) {
+			err = -ENOMEM;
+			goto free;
+		}
+	}
+
 	return 0;
 
 free:
@@ -7778,6 +7840,21 @@ static int sctp_msghdr_parse(const struct msghdr *msg, struct sctp_cmsgs *cmsgs)
 			if (cmsgs->prinfo->pr_policy == SCTP_PR_SCTP_NONE)
 				cmsgs->prinfo->pr_value = 0;
 			break;
+		case SCTP_DSTADDRV4:
+		case SCTP_DSTADDRV6:
+			/* SCTP Socket API Extension
+			 * 5.3.9/10 SCTP Destination IPv4/6 Address Structure (SCTP_DSTADDRV4/6)
+			 *
+			 * This cmsghdr structure specifies SCTP options for sendmsg().
+			 *
+			 * cmsg_level    cmsg_type         cmsg_data[]
+			 * ------------  ------------   ---------------------
+			 * IPPROTO_SCTP  SCTP_DSTADDRV4 struct in_addr
+			 * ------------  ------------   ---------------------
+			 * IPPROTO_SCTP  SCTP_DSTADDRV6 struct in6_addr
+			 */
+			cmsgs->addrs_msg = my_msg;
+			break;
 		default:
 			return -EINVAL;
 		}