recvfrom

Implemented in Antinomie 0.7.0 · Syscall list

Synopsis

long recvfrom(int fd, void *ubuf, size_t size, unsigned int flags, struct sockaddr *addr, int *addr_len);

Number (x86-64)	45
ABI	64
Kernel entry point	sys_recvfrom

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

Description

Receives data from a socket, optionally storing the sender’s address.

Arguments

Name	Type	Meaning
fd (arg0)	int	File descriptor to operate on.
ubuf (arg1)	void *	Buffer that receives the data.
size (arg2)	size_t	Size of that buffer.
flags (arg3)	unsigned int	Option flags that change the behavior of the call.
addr (arg4)	struct sockaddr *	Buffer for the sender address, or NULL.
addr_len (arg5)	int *	Pointer to the size of the address buffer; updated by the kernel.

Return value

On success: The number of bytes transferred (see the description for what 0 means).

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
-11	EAGAIN	The call would block, or a resource is temporarily unavailable.
-111	ECONNREFUSED	The connection was refused.
-4	EINTR	The call was interrupted by a signal.

Man page

recvfrom(2) on man7.org

Captured by Antinomie

Coverage mark: Implemented. Every pointer argument has a capture rule in the pinned kernel patch and none of them records a “no decoder”, “address only” or “not observed” gap on any code path. Individual values can still be incomplete on a particular call; see the capture statuses.

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
ubuf (arg1)	Entry	the pointer itself, as a raw word	args.1, args.raw[1]
↳ pointee	Exit	buffer; length min(result, size, MAX_RW_COUNT)	arg1.data	result is greater than 0
size (arg2)	Entry	raw scalar word	args.2, args.size
flags (arg3)	Entry	raw scalar word; Syscall Trace also decodes it into flag names (message group), listing unknown bits separately	args.3, args.flags
addr (arg4)	Entry	the pointer itself, as a raw word	args.4, args.raw[4]
↳ pointee	Exit	socket address (sockaddr layout), length min(written length, capacity)	address.data	result is 0 or greater and both pointers are set
addr_len (arg5)	Entry	the pointer itself, as a raw word	args.5, args.raw[5]
↳ pointee	Entry	socklen_t value the program provides	address.capacity	the length pointer is not NULL
↳ pointee	Exit	socklen_t value the kernel wrote	address.length	result is 0 or greater and both pointers are set

Filter fields

• Result: ret, syscall.errno, syscall.success, syscall.duration_ns.
• Argument words: args.fd (arg0), args.ubuf (arg1), args.size (arg2), args.flags (arg3), args.addr (arg4), args.addr_len (arg5); args.0 to args.5 by position.
• Structure sockaddr behind addr (arg4): args.addr.<member> for sa_family.
• Structure wait_status behind addr_len (arg5): args.addr_len.<member> for value.

See Syscall Trace filter for the full syntax.

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