Skip to content

[3.14] gh-154324: Fix os.sendfile() error reporting on illumos (GH-154327) #154833

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
serhiy-storchaka merged 1 commit into from
Jul 28, 2026
Merged

[3.14] gh-154324: Fix os.sendfile() error reporting on illumos (GH-154327) #154833

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
gh-154324: Fix os.sendfile() error reporting on illumos (GH-154327) 
illumos sendfile(3EXT) returns the number of transferred bytes by adding
it to the offset without initializing it, so the offset cannot be used to
detect a partial write.  Use sendfilev(3EXT), which reports the number of
transferred bytes in an explicit out parameter.
(cherry picked from commit e3634bb)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
  • Loading branch information
@serhiy-storchaka @claude @miss-islington
2 people authored and miss-islington committed Jul 28, 2026
commit a05ed237e635c74c7078c75a6daad4edfbadd86d
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-07-21-08-31-55.gh-issue-154324.vDxV5U.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix :func:`os.sendfile` on illumos:
it no longer reports a successful transfer
when the underlying system call failed without writing any data.
38 changes: 23 additions & 15 deletions Modules/posixmodule.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12095,27 +12095,35 @@ os_sendfile_impl(PyObject *module, int out_fd, int in_fd, PyObject *offobj,
return PyLong_FromLong(0);
}

// On illumos specifically sendfile() may perform a partial write but
// return -1/an error (in one confirmed case the destination socket
// had a 5 second timeout set and errno was EAGAIN) and it's on the client
// code to check if the offset parameter was modified by sendfile().
//
// We need this variable to track said change.
off_t original_offset = offset;
#endif
// sendfile() may perform a partial write and still return -1, so the
// number of transferred bytes must be taken from the out parameter.
// sendfile() reports it by adding it to the offset, but does not
// initialize it when the transfer fails before writing any data, so use
// sendfilev(), which reports it explicitly.
sendfilevec_t vec;
size_t xferred;

vec.sfv_fd = in_fd;
vec.sfv_flag = 0;
vec.sfv_off = offset;
vec.sfv_len = count;

do {
Py_BEGIN_ALLOW_THREADS
ret = sendfile(out_fd, in_fd, &offset, count);
#if defined(__sun) && defined(__SVR4)
// This handles illumos-specific sendfile() partial write behavior,
// see a comment above for more details.
if (ret < 0 && offset != original_offset) {
ret = offset - original_offset;
xferred = 0;
ret = sendfilev(out_fd, &vec, 1, &xferred);
if (ret < 0 && xferred != 0) {
ret = (Py_ssize_t)xferred;
}
#endif
Py_END_ALLOW_THREADS
} while (ret < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
#else
do {
Py_BEGIN_ALLOW_THREADS
ret = sendfile(out_fd, in_fd, &offset, count);
Py_END_ALLOW_THREADS
} while (ret < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
#endif
if (ret < 0)
return (!async_err) ? posix_error() : NULL;
return PyLong_FromSsize_t(ret);
Expand Down
Loading