[libc-commits] [libc] 12c36c7 - [libc] Implement if_nametoindex and if_indextoname (#206082)
via libc-commits
libc-commits at lists.llvm.org
Tue Jul 7 04:26:15 PDT 2026
Author: Pavel Labath
Date: 2026-07-07T11:26:10Z
New Revision: 12c36c7abb1600638d976258c1c0d3517df59226
URL: https://github.com/llvm/llvm-project/commit/12c36c7abb1600638d976258c1c0d3517df59226
DIFF: https://github.com/llvm/llvm-project/commit/12c36c7abb1600638d976258c1c0d3517df59226.diff
LOG: [libc] Implement if_nametoindex and if_indextoname (#206082)
This patch implements if_nametoindex and if_indextoname for Linux.
Both functions work by creating a temporary AF_UNIX socket and issuing
ioctl calls (SIOCGIFINDEX and SIOCGIFNAME, respectively).
The main implementation details:
- for if_nametoindex, I check that the interface name fits within
IF_NAMESIZE before issuing the ioctl
- for if_indextoname, if the kernel returns ENODEV for an unknown index,
I map it to ENXIO to comply with POSIX requirements
- added the definition of struct ifreq to support these operations.
Similar to the other net structure definitions, I'm using an anonymous
union to avoid #defining members.
Assisted by Gemini.
Added:
libc/hdr/net_if_macros.h
libc/hdr/types/struct_ifreq.h
libc/include/llvm-libc-macros/linux/net-if-macros.h
libc/include/llvm-libc-macros/net-if-macros.h
libc/include/llvm-libc-types/struct_ifreq.h
libc/include/net/if.yaml
libc/src/net/CMakeLists.txt
libc/src/net/if_indextoname.h
libc/src/net/if_nametoindex.h
libc/src/net/linux/CMakeLists.txt
libc/src/net/linux/if_indextoname.cpp
libc/src/net/linux/if_nametoindex.cpp
libc/test/src/net/CMakeLists.txt
libc/test/src/net/linux/CMakeLists.txt
libc/test/src/net/linux/if_indextoname_test.cpp
libc/test/src/net/linux/if_nametoindex_test.cpp
Modified:
libc/config/linux/aarch64/entrypoints.txt
libc/config/linux/riscv/entrypoints.txt
libc/config/linux/x86_64/entrypoints.txt
libc/hdr/CMakeLists.txt
libc/hdr/types/CMakeLists.txt
libc/include/CMakeLists.txt
libc/include/llvm-libc-macros/CMakeLists.txt
libc/include/llvm-libc-macros/linux/CMakeLists.txt
libc/include/llvm-libc-types/CMakeLists.txt
libc/src/CMakeLists.txt
libc/test/src/CMakeLists.txt
Removed:
################################################################################
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 04674d9247b87..af89add35f01e 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -1033,6 +1033,10 @@ if(LLVM_LIBC_FULL_BUILD)
libc.src.arpa.inet.ntohl
libc.src.arpa.inet.ntohs
+ # net/if.h entrypoints
+ libc.src.net.if_indextoname
+ libc.src.net.if_nametoindex
+
# netinet/in.h entrypoints
libc.src.netinet.in6addr_any
libc.src.netinet.in6addr_loopback
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index 7bb3f74add5c2..15e774fb453b7 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -1167,6 +1167,10 @@ if(LLVM_LIBC_FULL_BUILD)
libc.src.arpa.inet.ntohl
libc.src.arpa.inet.ntohs
+ # net/if.h entrypoints
+ libc.src.net.if_indextoname
+ libc.src.net.if_nametoindex
+
# netinet/in.h entrypoints
libc.src.netinet.in6addr_any
libc.src.netinet.in6addr_loopback
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 528532d96c7fb..ae457e1cb79e0 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -42,6 +42,10 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.fcntl.open
libc.src.fcntl.openat
+ # net/if.h entrypoints
+ libc.src.net.if_indextoname
+ libc.src.net.if_nametoindex
+
# netinet/in.h entrypoints
libc.src.netinet.in6addr_any
libc.src.netinet.in6addr_loopback
diff --git a/libc/hdr/CMakeLists.txt b/libc/hdr/CMakeLists.txt
index d67208b05a018..3558019e50608 100644
--- a/libc/hdr/CMakeLists.txt
+++ b/libc/hdr/CMakeLists.txt
@@ -86,6 +86,15 @@ add_proxy_header_library(
libc.include.llvm-libc-macros.inet_address_macros
)
+add_proxy_header_library(
+ net_if_macros
+ HDRS
+ net_if_macros.h
+ FULL_BUILD_DEPENDS
+ libc.include.net_if
+ libc.include.llvm-libc-macros.net_if_macros
+)
+
add_proxy_header_library(
netinet_in_macros
HDRS
diff --git a/libc/hdr/net_if_macros.h b/libc/hdr/net_if_macros.h
new file mode 100644
index 0000000000000..d70322dd8c71c
--- /dev/null
+++ b/libc/hdr/net_if_macros.h
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Definition of macros from net/if.h.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_HDR_NET_IF_MACROS_H
+#define LLVM_LIBC_HDR_NET_IF_MACROS_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-macros/net-if-macros.h"
+
+#else // Overlay mode
+
+#include <net/if.h>
+
+#endif // LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_NET_IF_MACROS_H
diff --git a/libc/hdr/types/CMakeLists.txt b/libc/hdr/types/CMakeLists.txt
index cc985933df5ea..6c645e1b1eb84 100644
--- a/libc/hdr/types/CMakeLists.txt
+++ b/libc/hdr/types/CMakeLists.txt
@@ -538,6 +538,15 @@ add_proxy_header_library(
libc.include.arpa_inet
)
+add_proxy_header_library(
+ struct_ifreq
+ HDRS
+ struct_ifreq.h
+ FULL_BUILD_DEPENDS
+ libc.include.llvm-libc-types.struct_ifreq
+ libc.include.net_if
+)
+
add_proxy_header_library(
struct_sockaddr
HDRS
diff --git a/libc/hdr/types/struct_ifreq.h b/libc/hdr/types/struct_ifreq.h
new file mode 100644
index 0000000000000..3f34ffa4a9d7c
--- /dev/null
+++ b/libc/hdr/types/struct_ifreq.h
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Proxy for struct ifreq.
+///
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_LIBC_HDR_TYPES_STRUCT_IFREQ_H
+#define LLVM_LIBC_HDR_TYPES_STRUCT_IFREQ_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-types/struct_ifreq.h"
+
+#else
+
+#include <net/if.h>
+
+#endif // LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_TYPES_STRUCT_IFREQ_H
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 885f94b725819..57310e6c6291b 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -896,6 +896,18 @@ add_header_macro(
.llvm-libc-types.siginfo_t
)
+file(MAKE_DIRECTORY ${LIBC_INCLUDE_DIR}/net)
+
+add_header_macro(
+ net_if
+ ../libc/include/net/if.yaml
+ net/if.h
+ DEPENDS
+ .llvm_libc_common_h
+ .llvm-libc-macros.net_if_macros
+ .llvm-libc-types.struct_ifreq
+)
+
# TODO: This should be conditional on POSIX networking being included.
file(MAKE_DIRECTORY ${LIBC_INCLUDE_DIR}/netinet)
diff --git a/libc/include/llvm-libc-macros/CMakeLists.txt b/libc/include/llvm-libc-macros/CMakeLists.txt
index 892f2a8b5b198..8f21d9811a160 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/CMakeLists.txt
@@ -314,6 +314,12 @@ add_macro_header(
sys-socket-macros.h
)
+add_macro_header(
+ net_if_macros
+ HDR
+ net-if-macros.h
+)
+
add_macro_header(
sys_time_macros
HDR
diff --git a/libc/include/llvm-libc-macros/linux/CMakeLists.txt b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
index c97270413197e..374e7e6159a5d 100644
--- a/libc/include/llvm-libc-macros/linux/CMakeLists.txt
+++ b/libc/include/llvm-libc-macros/linux/CMakeLists.txt
@@ -64,6 +64,12 @@ add_header(
sys-socket-macros.h
)
+add_header(
+ net_if_macros
+ HDR
+ net-if-macros.h
+)
+
add_header(
sys_wait_macros
HDR
diff --git a/libc/include/llvm-libc-macros/linux/net-if-macros.h b/libc/include/llvm-libc-macros/linux/net-if-macros.h
new file mode 100644
index 0000000000000..b5cd2c2ef144d
--- /dev/null
+++ b/libc/include/llvm-libc-macros/linux/net-if-macros.h
@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Macros defined in net/if.h header file.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_MACROS_LINUX_NET_IF_MACROS_H
+#define LLVM_LIBC_MACROS_LINUX_NET_IF_MACROS_H
+
+#define IF_NAMESIZE 16
+
+#endif // LLVM_LIBC_MACROS_LINUX_NET_IF_MACROS_H
diff --git a/libc/include/llvm-libc-macros/net-if-macros.h b/libc/include/llvm-libc-macros/net-if-macros.h
new file mode 100644
index 0000000000000..4af2b0bf401d5
--- /dev/null
+++ b/libc/include/llvm-libc-macros/net-if-macros.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Macros defined in net/if.h header file.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_MACROS_NET_IF_MACROS_H
+#define LLVM_LIBC_MACROS_NET_IF_MACROS_H
+
+#ifdef __linux__
+#include "linux/net-if-macros.h"
+#endif
+
+#endif // LLVM_LIBC_MACROS_NET_IF_MACROS_H
diff --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
index d4d75e9934626..5ea8ca0634834 100644
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -226,6 +226,7 @@ add_header(
)
add_header(struct_sockaddr_storage HDR struct_sockaddr_storage.h DEPENDS .sa_family_t)
add_header(struct_sockaddr_un HDR struct_sockaddr_un.h DEPENDS .sa_family_t)
+add_header(struct_ifreq HDR struct_ifreq.h DEPENDS libc.include.llvm-libc-macros.net_if_macros .struct_sockaddr)
add_header(struct_iovec HDR struct_iovec.h DEPENDS .size_t)
add_header(struct_linger HDR struct_linger.h)
add_header(struct_cmsghdr HDR struct_cmsghdr.h DEPENDS .size_t)
diff --git a/libc/include/llvm-libc-types/struct_ifreq.h b/libc/include/llvm-libc-types/struct_ifreq.h
new file mode 100644
index 0000000000000..b9ad182f97802
--- /dev/null
+++ b/libc/include/llvm-libc-types/struct_ifreq.h
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Definition of struct ifreq.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_TYPES_STRUCT_IFREQ_H
+#define LLVM_LIBC_TYPES_STRUCT_IFREQ_H
+
+#include "../llvm-libc-macros/net-if-macros.h"
+#include "struct_sockaddr.h"
+
+struct ifreq {
+ char ifr_name[IF_NAMESIZE];
+ __extension__ union {
+ struct sockaddr ifr_hwaddr;
+ struct sockaddr ifr_addr;
+ struct sockaddr ifr_dstaddr;
+ struct sockaddr ifr_broadaddr;
+ struct sockaddr ifr_netmask;
+ short int ifr_flags;
+ int ifr_metric;
+ int ifr_mtu;
+ int ifr_ifindex;
+ int ifr_bandwidth;
+ int ifr_qlen;
+ char ifr_newname[IF_NAMESIZE];
+ char ifr_slave[IF_NAMESIZE];
+ char *ifr_data;
+ };
+};
+
+#endif // LLVM_LIBC_TYPES_STRUCT_IFREQ_H
diff --git a/libc/include/net/if.yaml b/libc/include/net/if.yaml
new file mode 100644
index 0000000000000..51034d84e4428
--- /dev/null
+++ b/libc/include/net/if.yaml
@@ -0,0 +1,24 @@
+header: net/if.h
+standards:
+ - posix
+macros:
+ - macro_name: IF_NAMESIZE
+ macro_header: net-if-macros.h
+types:
+ - type_name: struct_ifreq
+enums: []
+objects: []
+functions:
+ - name: if_indextoname
+ standards:
+ - posix
+ return_type: char *
+ arguments:
+ - type: unsigned int
+ - type: char *
+ - name: if_nametoindex
+ standards:
+ - posix
+ return_type: unsigned int
+ arguments:
+ - type: const char *
diff --git a/libc/src/CMakeLists.txt b/libc/src/CMakeLists.txt
index 62aa164b35ee7..6ada1bef26a88 100644
--- a/libc/src/CMakeLists.txt
+++ b/libc/src/CMakeLists.txt
@@ -10,6 +10,7 @@ add_subdirectory(inttypes)
add_subdirectory(libgen)
add_subdirectory(link)
add_subdirectory(math)
+add_subdirectory(net)
add_subdirectory(netinet)
add_subdirectory(stdbit)
add_subdirectory(stdfix)
diff --git a/libc/src/net/CMakeLists.txt b/libc/src/net/CMakeLists.txt
new file mode 100644
index 0000000000000..2173a111cff4f
--- /dev/null
+++ b/libc/src/net/CMakeLists.txt
@@ -0,0 +1,17 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+ add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
+add_entrypoint_object(
+ if_indextoname
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.if_indextoname
+)
+
+add_entrypoint_object(
+ if_nametoindex
+ ALIAS
+ DEPENDS
+ .${LIBC_TARGET_OS}.if_nametoindex
+)
diff --git a/libc/src/net/if_indextoname.h b/libc/src/net/if_indextoname.h
new file mode 100644
index 0000000000000..215535328fbee
--- /dev/null
+++ b/libc/src/net/if_indextoname.h
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation header for if_indextoname.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_NET_IF_INDEXTONAME_H
+#define LLVM_LIBC_SRC_NET_IF_INDEXTONAME_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+char *if_indextoname(unsigned int ifindex, char *ifname);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_NET_IF_INDEXTONAME_H
diff --git a/libc/src/net/if_nametoindex.h b/libc/src/net/if_nametoindex.h
new file mode 100644
index 0000000000000..c3b27986cc5e7
--- /dev/null
+++ b/libc/src/net/if_nametoindex.h
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation header for if_nametoindex.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_NET_IF_NAMETOINDEX_H
+#define LLVM_LIBC_SRC_NET_IF_NAMETOINDEX_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+unsigned int if_nametoindex(const char *ifname);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_NET_IF_NAMETOINDEX_H
diff --git a/libc/src/net/linux/CMakeLists.txt b/libc/src/net/linux/CMakeLists.txt
new file mode 100644
index 0000000000000..9c82636d1c54c
--- /dev/null
+++ b/libc/src/net/linux/CMakeLists.txt
@@ -0,0 +1,44 @@
+add_entrypoint_object(
+ if_indextoname
+ SRCS
+ if_indextoname.cpp
+ HDRS
+ ../if_indextoname.h
+ DEPENDS
+ libc.hdr.net_if_macros
+ libc.hdr.errno_macros
+ libc.hdr.sys_ioctl_macros
+ libc.hdr.sys_socket_macros
+ libc.hdr.types.struct_ifreq
+ libc.src.__support.CPP.string_view
+ libc.src.__support.common
+ libc.src.__support.macros.null_check
+ libc.src.__support.OSUtil.linux.syscall_wrappers.socket
+ libc.src.__support.OSUtil.linux.syscall_wrappers.ioctl
+ libc.src.__support.OSUtil.linux.syscall_wrappers.close
+ libc.src.errno.errno
+ libc.src.string.memory_utils.inline_memcpy
+ libc.src.string.string_utils
+)
+
+add_entrypoint_object(
+ if_nametoindex
+ SRCS
+ if_nametoindex.cpp
+ HDRS
+ ../if_nametoindex.h
+ DEPENDS
+ libc.hdr.net_if_macros
+ libc.hdr.errno_macros
+ libc.hdr.sys_ioctl_macros
+ libc.hdr.sys_socket_macros
+ libc.hdr.types.struct_ifreq
+ libc.src.__support.CPP.string_view
+ libc.src.__support.common
+ libc.src.__support.macros.null_check
+ libc.src.__support.OSUtil.linux.syscall_wrappers.socket
+ libc.src.__support.OSUtil.linux.syscall_wrappers.ioctl
+ libc.src.__support.OSUtil.linux.syscall_wrappers.close
+ libc.src.errno.errno
+ libc.src.string.memory_utils.inline_memcpy
+)
diff --git a/libc/src/net/linux/if_indextoname.cpp b/libc/src/net/linux/if_indextoname.cpp
new file mode 100644
index 0000000000000..b97702ccde4b1
--- /dev/null
+++ b/libc/src/net/linux/if_indextoname.cpp
@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Linux implementation of if_indextoname.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/net/if_indextoname.h"
+#include "hdr/errno_macros.h"
+#include "hdr/net_if_macros.h"
+#include "hdr/sys_ioctl_macros.h"
+#include "hdr/sys_socket_macros.h"
+#include "hdr/types/struct_ifreq.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/close.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/ioctl.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/socket.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/null_check.h"
+#include "src/string/memory_utils/inline_memcpy.h"
+#include "src/string/string_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(char *, if_indextoname,
+ (unsigned int ifindex, char *ifname)) {
+ LIBC_CRASH_ON_NULLPTR(ifname);
+
+ ErrorOr<int> fd =
+ linux_syscalls::socket(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+ if (!fd.has_value()) {
+ libc_errno = fd.error();
+ return nullptr;
+ }
+
+ struct ifreq ifr;
+ ifr.ifr_ifindex = static_cast<int>(ifindex);
+
+ ErrorOr<int> ioctl_res = linux_syscalls::ioctl(*fd, SIOCGIFNAME, &ifr);
+
+ if (ErrorOr<int> res = linux_syscalls::close(*fd); !res.has_value()) {
+ libc_errno = res.error();
+ return nullptr;
+ }
+
+ if (!ioctl_res.has_value()) {
+ // Map kernel ENODEV to POSIX-mandated ENXIO.
+ libc_errno = (ioctl_res.error() == ENODEV) ? ENXIO : ioctl_res.error();
+ return nullptr;
+ }
+
+ cpp::string_view k_name(
+ ifr.ifr_name, internal::strnlen(ifr.ifr_name, sizeof(ifr.ifr_name)));
+ inline_memcpy(ifname, k_name.data(), k_name.size());
+ // Linux kernel does allow network devices exactly IF_NAMESIZE long (it leaves
+ // room for the terminating \0). But if that happens, let's not overrun the
+ // user provided buffer.
+ if (k_name.size() < IF_NAMESIZE)
+ ifname[k_name.size()] = '\0';
+
+ return ifname;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/net/linux/if_nametoindex.cpp b/libc/src/net/linux/if_nametoindex.cpp
new file mode 100644
index 0000000000000..a75db2d85daa7
--- /dev/null
+++ b/libc/src/net/linux/if_nametoindex.cpp
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Linux implementation of if_nametoindex.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/net/if_nametoindex.h"
+#include "hdr/errno_macros.h"
+#include "hdr/net_if_macros.h"
+#include "hdr/sys_ioctl_macros.h"
+#include "hdr/sys_socket_macros.h"
+#include "hdr/types/struct_ifreq.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/close.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/ioctl.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/socket.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/null_check.h"
+#include "src/string/memory_utils/inline_memcpy.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(unsigned int, if_nametoindex, (const char *ifname)) {
+ LIBC_CRASH_ON_NULLPTR(ifname);
+
+ cpp::string_view name(ifname);
+ if (name.empty() || name.size() >= IF_NAMESIZE) {
+ libc_errno = ENODEV;
+ return 0;
+ }
+
+ ErrorOr<int> fd =
+ linux_syscalls::socket(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+ if (!fd.has_value()) {
+ libc_errno = fd.error();
+ return 0;
+ }
+
+ struct ifreq ifr;
+ inline_memcpy(ifr.ifr_name, name.data(), name.size() + 1);
+
+ ErrorOr<int> ioctl_res = linux_syscalls::ioctl(*fd, SIOCGIFINDEX, &ifr);
+
+ if (ErrorOr<int> res = linux_syscalls::close(*fd); !res.has_value()) {
+ libc_errno = res.error();
+ return 0;
+ }
+
+ if (!ioctl_res.has_value()) {
+ libc_errno = ioctl_res.error();
+ return 0;
+ }
+
+ return static_cast<unsigned int>(ifr.ifr_ifindex);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/CMakeLists.txt b/libc/test/src/CMakeLists.txt
index 45815c9bba8ca..077327d987dac 100644
--- a/libc/test/src/CMakeLists.txt
+++ b/libc/test/src/CMakeLists.txt
@@ -66,6 +66,7 @@ add_subdirectory(fenv)
add_subdirectory(libgen)
add_subdirectory(link)
add_subdirectory(math)
+add_subdirectory(net)
add_subdirectory(netinet)
add_subdirectory(search)
add_subdirectory(setjmp)
diff --git a/libc/test/src/net/CMakeLists.txt b/libc/test/src/net/CMakeLists.txt
new file mode 100644
index 0000000000000..8e285dd5b94c5
--- /dev/null
+++ b/libc/test/src/net/CMakeLists.txt
@@ -0,0 +1,4 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+ add_subdirectory(${LIBC_TARGET_OS})
+endif()
+
diff --git a/libc/test/src/net/linux/CMakeLists.txt b/libc/test/src/net/linux/CMakeLists.txt
new file mode 100644
index 0000000000000..c9119a954ad9c
--- /dev/null
+++ b/libc/test/src/net/linux/CMakeLists.txt
@@ -0,0 +1,27 @@
+add_custom_target(libc_net_unittests)
+
+add_libc_unittest(
+ if_indextoname_test
+ SUITE
+ libc_net_unittests
+ SRCS
+ if_indextoname_test.cpp
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.net_if_macros
+ libc.src.net.if_indextoname
+ libc.src.net.if_nametoindex
+ libc.test.UnitTest.ErrnoCheckingTest
+)
+
+add_libc_unittest(
+ if_nametoindex_test
+ SUITE
+ libc_net_unittests
+ SRCS
+ if_nametoindex_test.cpp
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.src.net.if_nametoindex
+ libc.test.UnitTest.ErrnoCheckingTest
+)
diff --git a/libc/test/src/net/linux/if_indextoname_test.cpp b/libc/test/src/net/linux/if_indextoname_test.cpp
new file mode 100644
index 0000000000000..6c7f3888e300a
--- /dev/null
+++ b/libc/test/src/net/linux/if_indextoname_test.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Unittests for if_indextoname.
+///
+//===----------------------------------------------------------------------===//
+
+#include "hdr/errno_macros.h"
+#include "hdr/net_if_macros.h"
+#include "src/net/if_indextoname.h"
+#include "src/net/if_nametoindex.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcIfIndexToNameTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+TEST_F(LlvmLibcIfIndexToNameTest, Loopback) {
+ unsigned int lo_idx = LIBC_NAMESPACE::if_nametoindex("lo");
+ ASSERT_GT(lo_idx, 0u);
+
+ char buf[IF_NAMESIZE];
+ char *res = LIBC_NAMESPACE::if_indextoname(lo_idx, buf);
+ ASSERT_EQ(res, buf);
+ ASSERT_STREQ(buf, "lo");
+ ASSERT_ERRNO_SUCCESS();
+}
+
+TEST_F(LlvmLibcIfIndexToNameTest, InvalidIndex) {
+ char buf[IF_NAMESIZE];
+ char *res = LIBC_NAMESPACE::if_indextoname(-1u, buf);
+ ASSERT_EQ(res, static_cast<char *>(nullptr));
+ ASSERT_ERRNO_EQ(ENXIO);
+}
+
+TEST_F(LlvmLibcIfIndexToNameTest, ZeroIndex) {
+ char buf[IF_NAMESIZE];
+ char *res = LIBC_NAMESPACE::if_indextoname(0u, buf);
+ ASSERT_EQ(res, static_cast<char *>(nullptr));
+ ASSERT_ERRNO_EQ(ENXIO);
+}
+
+TEST_F(LlvmLibcIfIndexToNameTest, NullPtrDeath) {
+ ASSERT_DEATH([]() { LIBC_NAMESPACE::if_indextoname(1u, nullptr); },
+ WITH_SIGNAL(-1));
+}
diff --git a/libc/test/src/net/linux/if_nametoindex_test.cpp b/libc/test/src/net/linux/if_nametoindex_test.cpp
new file mode 100644
index 0000000000000..353b781a018ee
--- /dev/null
+++ b/libc/test/src/net/linux/if_nametoindex_test.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Unittests for if_nametoindex.
+///
+//===----------------------------------------------------------------------===//
+
+#include "hdr/errno_macros.h"
+#include "src/net/if_nametoindex.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcIfNameToIndexTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
+TEST_F(LlvmLibcIfNameToIndexTest, Loopback) {
+ unsigned int idx = LIBC_NAMESPACE::if_nametoindex("lo");
+ ASSERT_GT(idx, 0u);
+ ASSERT_ERRNO_SUCCESS();
+}
+
+TEST_F(LlvmLibcIfNameToIndexTest, InvalidName) {
+ unsigned int idx = LIBC_NAMESPACE::if_nametoindex("nonexistent_if");
+ ASSERT_EQ(idx, 0u);
+ ASSERT_ERRNO_EQ(ENODEV);
+}
+
+TEST_F(LlvmLibcIfNameToIndexTest, EmptyName) {
+ unsigned int idx = LIBC_NAMESPACE::if_nametoindex("");
+ ASSERT_EQ(idx, 0u);
+ ASSERT_ERRNO_EQ(ENODEV);
+}
+
+TEST_F(LlvmLibcIfNameToIndexTest, NullPtrDeath) {
+ ASSERT_DEATH([]() { LIBC_NAMESPACE::if_nametoindex(nullptr); },
+ WITH_SIGNAL(-1));
+}
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