setsockopt

Partial in Antinomie 0.7.0 · Syscall list

Synopsis

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

Number (x86-64)	54
ABI	64
Kernel entry point	sys_setsockopt

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

Description

Sets an option on a socket or on a 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 *	Pointer to the option value.
optlen (arg4)	int	Size of the option value in bytes.

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

setsockopt(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 sockopt.unknown_option “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	the option value; known options use their layout (integers, linger, timeouts, interface names, congestion control names, membership structures); unknown (level, optname) pairs are raw bytes up to 128 KiB	arg3.optval	length from optlen (arg4); “invalid extent” on a size mismatch
↳ pointee	Entry	array of sock_filter instructions (8 bytes each)	arg3.optval.filter	SO_ATTACH_FILTER or SO_ATTACH_REUSEPORT_CBPF; “invalid extent” if the length is 0 or above 4,096
optlen (arg4)	Entry	raw scalar word	args.4, args.optlen

Family notes

• Selector: (level, optname). The value is recorded at entry as arg3.optval, with a known layout for known options (integers, linger, timeouts, socket filters with their instruction array, interface names, congestion control names).

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 sock_fprog behind optval (arg3): args.optval.<member> for filter, len.

See Syscall Trace filter for the full syntax.

Known gaps

• An unknown (level, optname) pair also records sockopt.unknown_option with the “no decoder” status; a few nested structures (netfilter table replacement, multicast source lists) keep only their top-level bytes.
• 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.