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Use net.DialUnix instead of net.Dial

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Using net.Dial makes the DNS resolver from the net package (including
vendor/golang.org/x/net/dns/dnsmessage) reachable for the linker, since
net.Dial can be used with a host name. All the runc callers only ever
connect to a unix socket, so use net.DialUnix, which does not do any
name resolution. As a bonus, there is no need for a type assertion to
call File().

On its own, this change does not make runc binary smaller, since
godbus/dbus also uses net.Dial in its tcp transports. Once godbus gets
a way to disable those (see https://github.com/godbus/dbus/pull/444),
the two changes together make runc binary about 380 KB (3.7%) smaller.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin
2026-10-05 15:53:46 -07:00
parent ea8b6d42cd
commit f61eed56ed
2 changed files with 6 additions and 6 deletions
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4
libcontainer/process_linux.go
View File

@@ -1117,13 +1117,13 @@ func pidGetFd(pid, srcFd int) (*os.File, error) {
}
func sendContainerProcessState(listenerPath string, state *specs.ContainerProcessState, file *os.File) error {
conn, err := net.Dial("unix", listenerPath)
conn, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: listenerPath, Net: "unix"})
if err != nil {
return fmt.Errorf("failed to connect with seccomp agent specified in the seccomp profile: %w", err)
}
defer conn.Close()
socket, err := conn.(*net.UnixConn).File()
socket, err := conn.File()
if err != nil {
return fmt.Errorf("cannot get seccomp socket: %w", err)
}

8
utils_linux.go
View File

@@ -119,7 +119,7 @@ func setupIO(process *libcontainer.Process, container *libcontainer.Container, c
}()
} else {
// the caller of runc will handle receiving the console master
conn, err := net.Dial("unix", sockpath)
conn, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: sockpath, Net: "unix"})
if err != nil {
return nil, err
}
@@ -129,7 +129,7 @@ func setupIO(process *libcontainer.Process, container *libcontainer.Container, c
}
}()
t.postStart = append(t.postStart, conn)
socket, err := conn.(*net.UnixConn).File()
socket, err := conn.File()
if err != nil {
return nil, err
}
@@ -441,12 +441,12 @@ func setupPidfdSocket(process *libcontainer.Process, sockpath string) (_clean fu
return nil, fmt.Errorf("--pidfd-socket requires >= v5.3 kernel")
}
conn, err := net.Dial("unix", sockpath)
conn, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: sockpath, Net: "unix"})
if err != nil {
return nil, fmt.Errorf("failed to dail %s: %w", sockpath, err)
}
socket, err := conn.(*net.UnixConn).File()
socket, err := conn.File()
if err != nil {
conn.Close()
return nil, fmt.Errorf("failed to dup socket: %w", err)