getsockopt

Partial in Antinomie 0.7.0 · Syscall list

Synopsis

long getsockopt(int fd, int level, int optname, char *optval, int *optlen);

Number (x86-64)	55
ABI	64
Kernel entry point	sys_getsockopt

This is the raw kernel prototype from the pinned Linux 6.12.94 schema, not the libc wrapper.

Description

Reads an option of a socket or protocol layer, identified by a level and an option name.

Arguments

Name	Type	Meaning
fd (arg0)	int	File descriptor to operate on.
level (arg1)	int	Protocol level, SOL_SOCKET (1) or a protocol number such as IPPROTO_TCP (6).
optname (arg2)	int	Option name within the level.
optval (arg3)	char *	Buffer the kernel fills with the option value.
optlen (arg4)	int *	Pointer to the buffer size; the kernel writes the real size back.

Return value

On success: 0.

In an Antinomie trace the Return column and the ret filter field show the raw kernel return value. On failure that is the negative errno, for example -2 for ENOENT, not the -1 plus errno that the libc wrapper gives. syscall.errno holds the positive errno and syscall.success is false.

Common errors

Raw return	Name	Meaning
-9	EBADF	A file descriptor is not valid for this operation.
-22	EINVAL	An argument is invalid.
-92	ENOPROTOOPT	The protocol does not support this option.

Man page

getsockopt(2) on man7.org

Captured by Antinomie

Coverage mark: Partial. Known (level, option) pairs decode their value. An unknown pair records the raw bytes (up to 128 KiB) together with a “no decoder” gap, and a few nested structures are left raw.

Every call is recorded as an Entry record (the six argument words and the pointees copied at entry) and an Exit record (the return value and the pointees copied at exit).

Arguments

Argument	When	How	Recorded field key	Condition
fd (arg0)	Entry	raw scalar word	args.0, args.fd
level (arg1)	Entry	raw scalar word	args.1, args.level
optname (arg2)	Entry	raw scalar word	args.2, args.optname
optval (arg3)	Entry	the pointer itself, as a raw word	args.3, args.raw[3]
↳ pointee	Entry	input value for the few options that also read one	arg3.optval_in	the option has an input layout
↳ pointee	Exit	the option value; known options use their layout, unknown pairs are raw bytes up to 128 KiB; length is the written length	arg3.optval	result is 0; “invalid extent” if the written length exceeds the capacity
optlen (arg4)	Entry	the pointer itself, as a raw word	args.4, args.raw[4]
↳ pointee	Entry and exit	int: the buffer capacity at entry, and the length the kernel wrote at exit	arg4.optlen	at exit only when result is 0

Family notes

• Selector: (level, optname). arg4.optlen is recorded at entry as the capacity, and again at exit with the length the kernel wrote; arg3.optval is recorded at exit on success, bounded by the written length.

Filter fields

• Result: ret, syscall.errno, syscall.success, syscall.duration_ns.
• Argument words: args.fd (arg0), args.level (arg1), args.optname (arg2), args.optval (arg3), args.optlen (arg4); args.0 to args.5 by position.
• Structure tcp_zerocopy_receive behind optval (arg3): args.optval.<member> for address, copybuf_address, copybuf_len, err, flags, inq, length, msg_control, msg_controllen, msg_flags, recv_skip_hint, reserved.
• Structure wait_status behind optlen (arg4): args.optlen.<member> for value.

See Syscall Trace filter for the full syntax.

Known gaps

• An unknown (level, optname) pair records sockopt.unknown_option with the “no decoder” status at entry.
• See the coverage mark above for the code paths that record a gap.

For what the capture statuses mean, see Capture statuses. For what is never recorded, see Known gaps.