net: Add a new socket option for a future transmit time.

This patch introduces SO_TXTIME. User space enables this option in order to pass a desired future transmit time in a CMSG when calling sendmsg(2). The argument to this socket option is a 8-bytes long struct provided by the uapi header net_tstamp.h defined as: struct sock_txtime { clockid_t clockid; u32 flags; }; Note that new fields were added to struct sock by filling a 2-bytes hole found in the struct. For that reason, neither the struct size or number of cachelines were altered.

Richard Cochran committed 8 years ago

Commit 80b14de1 parent c47d8c211 files · +84 −0Browse files

Showing the changes to include/uapi/linux (1 of 11 files). Show all

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include/uapi/linux/net_tstamp.h+15−0

@@ -141,4 +141,19 @@ struct scm_ts_pktinfo { · 140 unmodified lines
141	141	__u32 reserved[2];
142	142	};
143	143
	144	+/*
	145	+ * SO_TXTIME gets a struct sock_txtime with flags being an integer bit
	146	+ * field comprised of these values.
	147	+ */
	148	+enum txtime_flags {
	149	+ SOF_TXTIME_DEADLINE_MODE = (1 << 0),
	150	+
	151	+ SOF_TXTIME_FLAGS_MASK = (SOF_TXTIME_DEADLINE_MODE)
	152	+};
	153	+
	154	+struct sock_txtime {
	155	+ clockid_t clockid; /* reference clockid */
	156	+ u32 flags; /* flags defined by enum txtime_flags */
	157	+};
	158	+
144	159	#endif /* _NET_TIMESTAMPING_H */