Re: [PATCH net-next 2/3] sctp: add support for SCTP_DSTADDRV4/6 Information for sendmsg

[Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>]

On Mon, Mar 05, 2018 at 08:44:19PM +0800, Xin Long wrote:
> 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>
> ---
>  include/net/sctp/structs.h |  1 +
>  include/uapi/linux/sctp.h  |  6 ++++
>  net/sctp/socket.c          | 77 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 84 insertions(+)
> 
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index d40a2a3..ec6e46b 100644
> --- a/include/net/sctp/structs.h
> +++ b/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 */
> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> index 0dd1f82..a1bc350 100644
> --- a/include/uapi/linux/sctp.h
> +++ b/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;
>  
>  /*
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index fdde697..067b57a 100644
> --- a/net/sctp/socket.c
> +++ b/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;

I think this is being handled differently from what the RFC specifies.
AFAIU the rfc defines these two options being each one an array of a
specific element type, in_addr and in6_addr.

The patch is saving both options into a single pointer, which later is
processed as a list of (in_addr or in6_addr) elements.

If an application specifies both options, each with a list of its own
addresses, it will ignore one of the options.

> +			break;
>  		default:
>  			return -EINVAL;
>  		}
> -- 
> 2.1.0
>