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mptcp: add MPTCP_SUBFLOW_ADDRS getsockopt support

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This retrieves the address pairs of all subflows currently
active for a given mptcp connection.

It re-uses the same meta-header as for MPTCP_TCPINFO.

A new structure is provided to hold the subflow
address data:

struct mptcp_subflow_addrs {
	union {
		__kernel_sa_family_t sa_family;
		struct sockaddr sa_local;
		struct sockaddr_in sin_local;
		struct sockaddr_in6 sin6_local;
		struct sockaddr_storage ss_local;
	};
	union {
		struct sockaddr sa_remote;
		struct sockaddr_in sin_remote;
		struct sockaddr_in6 sin6_remote;
		struct sockaddr_storage ss_remote;
	};
};

Usage of the new getsockopt is very similar to
MPTCP_TCPINFO one.

Userspace allocates a
'struct mptcp_subflow_data', followed by one or
more 'struct mptcp_subflow_addrs', then inits the
mptcp_subflow_data structure as follows:

struct mptcp_subflow_addrs *sf_addr;
struct mptcp_subflow_data *addr;
socklen_t olen = sizeof(*addr) + (8 * sizeof(*sf_addr));

addr = malloc(olen);
addr->size_subflow_data = sizeof(*addr);
addr->num_subflows = 0;
addr->size_kernel = 0;
addr->size_user = sizeof(struct mptcp_subflow_addrs);

sf_addr = (struct mptcp_subflow_addrs *)(addr + 1);

and then retrieves the endpoint addresses via:
ret = getsockopt(fd, SOL_MPTCP, MPTCP_SUBFLOW_ADDRS,
		 addr, &olen);

If the call succeeds, kernel will have added up to 8
endpoint addresses after the 'mptcp_subflow_data' header.

Userspace needs to re-check 'olen' value to detect how
many bytes have been filled in by the kernel.

Userspace can check addr->num_subflows to discover when
there were more subflows that available data space.

Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal
2021-09-17 16:33:21 -07:00
committed by David S. Miller
parent 06f15cee36
commit c11c5906bc
2 changed files with 115 additions and 0 deletions
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24
include/uapi/linux/mptcp.h
View File

@@ -4,6 +4,13 @@
#include <linux/const.h>
#include <linux/types.h>
#include <linux/in.h> /* for sockaddr_in */
#include <linux/in6.h> /* for sockaddr_in6 */
#include <linux/socket.h> /* for sockaddr_storage and sa_family */
#ifndef __KERNEL__
#include <sys/socket.h> /* for struct sockaddr */
#endif
#define MPTCP_SUBFLOW_FLAG_MCAP_REM _BITUL(0)
#define MPTCP_SUBFLOW_FLAG_MCAP_LOC _BITUL(1)
@@ -200,8 +207,25 @@ struct mptcp_subflow_data {
__u32 size_user; /* size of one element in data[] */
} __attribute__((aligned(8)));
struct mptcp_subflow_addrs {
union {
__kernel_sa_family_t sa_family;
struct sockaddr sa_local;
struct sockaddr_in sin_local;
struct sockaddr_in6 sin6_local;
struct __kernel_sockaddr_storage ss_local;
};
union {
struct sockaddr sa_remote;
struct sockaddr_in sin_remote;
struct sockaddr_in6 sin6_remote;
struct __kernel_sockaddr_storage ss_remote;
};
};
/* MPTCP socket options */
#define MPTCP_INFO 1
#define MPTCP_TCPINFO 2
#define MPTCP_SUBFLOW_ADDRS 3
#endif /* _UAPI_MPTCP_H */