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Handle new representation of abstract UDS paths.

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When abstract unix domain socket paths are displayed in
/proc/net/unix, Linux historically emitted null bytes as padding at
the end of the path. Newer versions of Linux (v4.9,
e7947ea770d0de434d38a0f823e660d3fd4bebb5) display these as '@'
characters.

Update proc_net_unix test to handle both version of the padding.

PiperOrigin-RevId: 266230200
This commit is contained in:
Rahat Mahmood
2019-08-29 14:37:47 -07:00
committed by gVisor bot
parent 863e11ac4d
commit f74affe203
1 changed files with 36 additions and 18 deletions
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test/syscalls/linux/proc_net_unix.cc
+36 -18
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@@ -56,19 +56,44 @@ struct UnixEntry {
std::string path;
};
// Abstract socket paths can have either trailing null bytes or '@'s as padding
// at the end, depending on the linux version. This function strips any such
// padding.
void StripAbstractPathPadding(std::string* s) {
const char pad_char = s->back();
if (pad_char != '\0' && pad_char != '@') {
return;
}
const auto last_pos = s->find_last_not_of(pad_char);
if (last_pos != std::string::npos) {
s->resize(last_pos + 1);
}
}
// Precondition: addr must be a unix socket address (i.e. sockaddr_un) and
// addr->sun_path must be null-terminated. This is always the case if addr comes
// from Linux:
//
// Per man unix(7):
//
// "When the address of a pathname socket is returned (by [getsockname(2)]), its
// length is
//
// offsetof(struct sockaddr_un, sun_path) + strlen(sun_path) + 1
//
// and sun_path contains the null-terminated pathname."
std::string ExtractPath(const struct sockaddr* addr) {
const char* path =
reinterpret_cast<const struct sockaddr_un*>(addr)->sun_path;
// Note: sockaddr_un.sun_path is an embedded character array of length
// UNIX_PATH_MAX, so we can always safely dereference the first 2 bytes below.
//
// The kernel also enforces that the path is always null terminated.
// We also rely on the path being null-terminated.
if (path[0] == 0) {
// Abstract socket paths are null padded to the end of the struct
// sockaddr. However, these null bytes may or may not show up in
// /proc/net/unix depending on the kernel version. Truncate after the first
// null byte (by treating path as a c-string).
return StrCat("@", &path[1]);
std::string abstract_path = StrCat("@", &path[1]);
StripAbstractPathPadding(&abstract_path);
return abstract_path;
}
return std::string(path);
}
@@ -96,14 +121,6 @@ PosixErrorOr<std::vector<UnixEntry>> ProcNetUnixEntries() {
continue;
}
// Abstract socket paths can have trailing null bytes in them depending on
// the linux version. Strip off everything after a null byte, including the
// null byte.
std::size_t null_pos = line.find('\0');
if (null_pos != std::string::npos) {
line.erase(null_pos);
}
// Parse a single entry from /proc/net/unix.
//
// Sample file:
@@ -151,6 +168,7 @@ PosixErrorOr<std::vector<UnixEntry>> ProcNetUnixEntries() {
entry.path = "";
if (fields.size() > 1) {
entry.path = fields[1];
StripAbstractPathPadding(&entry.path);
}
entries.push_back(entry);
@@ -200,8 +218,8 @@ TEST(ProcNetUnix, FilesystemBindAcceptConnect) {
std::string path1 = ExtractPath(sockets->first_addr());
std::string path2 = ExtractPath(sockets->second_addr());
std::cout << StreamFormat("Server socket address: %s\n", path1);
std::cout << StreamFormat("Client socket address: %s\n", path2);
std::cerr << StreamFormat("Server socket address (path1): %s\n", path1);
std::cerr << StreamFormat("Client socket address (path2): %s\n", path2);
std::vector<UnixEntry> entries =
ASSERT_NO_ERRNO_AND_VALUE(ProcNetUnixEntries());
@@ -224,8 +242,8 @@ TEST(ProcNetUnix, AbstractBindAcceptConnect) {
std::string path1 = ExtractPath(sockets->first_addr());
std::string path2 = ExtractPath(sockets->second_addr());
std::cout << StreamFormat("Server socket address: '%s'\n", path1);
std::cout << StreamFormat("Client socket address: '%s'\n", path2);
std::cerr << StreamFormat("Server socket address (path1): '%s'\n", path1);
std::cerr << StreamFormat("Client socket address (path2): '%s'\n", path2);
std::vector<UnixEntry> entries =
ASSERT_NO_ERRNO_AND_VALUE(ProcNetUnixEntries());