Reduce UDS/segment name clashes across same-service instances

CONTRIBUTORS

@@ -54,7 +54,7 @@ Thank you!
     Andrew Tridgell
     Andrey <[email protected]>
     Andrey Shorin <[email protected]>
-    ankor2023 <138755079+ankor2023@users.noreply.github.com>
+    Ankor <ankor2023@gmail.com>
     Anonymous <[email protected]>
     Anonymous <[email protected]>
     Anonymous Pootle User

src/Instance.cc

@@ -11,6 +11,7 @@
 #include "debug/Messages.h"
 #include "fs_io.h"
 #include "Instance.h"
+#include "md5.h"
 #include "parser/Tokenizer.h"
 #include "sbuf/Stream.h"
 #include "SquidConfig.h"
@@ -222,3 +223,43 @@ Instance::WriteOurPid()
     debugs(50, Important(23), "Created " << TheFile);
 }
 
+/// A hash that is likely to be unique across instances running on the same host
+/// because such concurrent instances should use unique PID filenames.
+/// All instances with disabled PID file maintenance have the same hash value.
+/// \returns a 4-character string suitable for use in file names and similar contexts
+static SBuf
+PidFilenameHash()
+{
+    uint8_t hash[SQUID_MD5_DIGEST_LENGTH];
+
+    SquidMD5_CTX ctx;
+    SquidMD5Init(&ctx);
+    const auto name = PidFilenameCalc();
+    SquidMD5Update(&ctx, name.rawContent(), name.length());
+    SquidMD5Final(hash, &ctx);
+
+    // converts raw hash byte at a given position to a filename-suitable character
+    const auto hashAt = [&hash](const size_t idx) {
+        const auto safeChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+        return safeChars[hash[idx] % strlen(safeChars)];
+    };
+
+    SBuf buf;
+    buf.appendf("%c%c%c%c", hashAt(0), hashAt(1), hashAt(2), hashAt(3));
+    return buf;
+}
+
+SBuf
+Instance::NamePrefix(const char * const head, const char * const tail)
+{
+    SBuf buf(head);
+    buf.append(service_name);
+    buf.append("-");
+    buf.append(PidFilenameHash());
+    if (tail) {
+        // TODO: Remove leading "-" from callers and explicitly add it here.
+        buf.append(tail);
+    }
+    return buf;
+}
+

src/Instance.h

@@ -9,6 +9,8 @@
 #ifndef SQUID_SRC_INSTANCE_H
 #define SQUID_SRC_INSTANCE_H
 
+#include "sbuf/forward.h"
+
 #if HAVE_SYS_TYPES_H
 #include <sys/types.h>
 #endif
@@ -30,6 +32,14 @@ void WriteOurPid();
 /// Throws if PID file maintenance is disabled.
 pid_t Other();
 
+/// A service_name-derived string that is likely to be unique across all Squid
+/// instances concurrently running on the same host (as long as they do not
+/// disable PID file maintenance).
+/// \param head is used at the beginning of the generated name
+/// \param tail is used at the end of the generated name (when not nil)
+/// \returns a head-...tail string suitable for making file and shm segment names
+SBuf NamePrefix(const char *head, const char *tail = nullptr);
+
 } // namespace Instance
 
 #endif /* SQUID_SRC_INSTANCE_H */

src/Makefile.am

@@ -1032,6 +1032,7 @@ tests_testRock_SOURCES = \
 	HttpHeaderTools.h \
 	HttpReply.cc \
 	tests/stub_HttpRequest.cc \
+	tests/stub_Instance.cc \
 	LogTags.cc \
 	MasterXaction.cc \
 	MasterXaction.h \
@@ -1202,6 +1203,7 @@ tests_testUfs_SOURCES = \
 	HttpHeaderTools.h \
 	HttpReply.cc \
 	tests/stub_HttpRequest.cc \
+	tests/stub_Instance.cc \
 	LogTags.cc \
 	MasterXaction.cc \
 	MasterXaction.h \
@@ -1374,6 +1376,7 @@ tests_testStore_SOURCES = \
 	HttpHeaderTools.h \
 	tests/stub_HttpReply.cc \
 	tests/stub_HttpRequest.cc \
+	tests/stub_Instance.cc \
 	MasterXaction.cc \
 	MasterXaction.h \
 	MemBuf.cc \
@@ -1537,6 +1540,7 @@ tests_testDiskIO_SOURCES = \
 	HttpHeaderTools.h \
 	HttpReply.cc \
 	tests/stub_HttpRequest.cc \
+	tests/stub_Instance.cc \
 	LogTags.cc \
 	MasterXaction.cc \
 	MasterXaction.h \
@@ -1800,6 +1804,7 @@ tests_testHttpRange_SOURCES = \
 	HttpReply.cc \
 	HttpRequest.cc \
 	tests/stub_HttpUpgradeProtocolAccess.cc \
+	tests/stub_Instance.cc \
 	IoStats.h \
 	tests/stub_IpcIoFile.cc \
 	LogTags.cc \
@@ -2060,6 +2065,7 @@ tests_testHttpReply_SOURCES = \
 	tests/testHttpReply.cc \
 	HttpReply.h \
 	tests/stub_HttpRequest.cc \
+	tests/stub_Instance.cc \
 	MasterXaction.cc \
 	MasterXaction.h \
 	MemBuf.cc \
@@ -2187,6 +2193,7 @@ tests_testHttpRequest_SOURCES = \
 	tests/testHttpRequest.cc \
 	tests/testHttpRequestMethod.cc \
 	tests/stub_HttpUpgradeProtocolAccess.cc \
+	tests/stub_Instance.cc \
 	IoStats.h \
 	tests/stub_IpcIoFile.cc \
 	LogTags.cc \
@@ -2484,6 +2491,7 @@ tests_testCacheManager_SOURCES = \
 	HttpReply.cc \
 	HttpRequest.cc \
 	tests/stub_HttpUpgradeProtocolAccess.cc \
+	tests/stub_Instance.cc \
 	IoStats.h \
 	tests/stub_IpcIoFile.cc \
 	LogTags.cc \

src/ipc/Port.cc

@@ -13,6 +13,7 @@
 #include "comm/Connection.h"
 #include "comm/Read.h"
 #include "CommCalls.h"
+#include "Instance.h"
 #include "ipc/Port.h"
 #include "sbuf/Stream.h"
 #include "tools.h"
@@ -52,9 +53,8 @@ bool Ipc::Port::doneAll() const
 String Ipc::Port::MakeAddr(const char* processLabel, int id)
 {
     assert(id >= 0);
-    String addr = channelPathPfx;
-    addr.append(service_name);
-    addr.append(processLabel);
+    String addr;
+    addr.append(Instance::NamePrefix(channelPathPfx, processLabel));
     addr.append('-');
     addr.append(xitoa(id));
     addr.append(".ipc");
@@ -66,9 +66,7 @@ Ipc::Port::CoordinatorAddr()
 {
     static String coordinatorAddr;
     if (!coordinatorAddr.size()) {
-        coordinatorAddr= channelPathPfx;
-        coordinatorAddr.append(service_name);
-        coordinatorAddr.append(coordinatorAddrLabel);
+        coordinatorAddr.append(Instance::NamePrefix(channelPathPfx, coordinatorAddrLabel));
         coordinatorAddr.append(".ipc");
     }
     return coordinatorAddr;

src/ipc/mem/Segment.cc

@@ -13,6 +13,7 @@
 #include "compat/shm.h"
 #include "debug/Stream.h"
 #include "fatal.h"
+#include "Instance.h"
 #include "ipc/mem/Segment.h"
 #include "sbuf/SBuf.h"
 #include "SquidConfig.h"
@@ -277,8 +278,7 @@ Ipc::Mem::Segment::GenerateName(const char *id)
         if (name[name.size()-1] != '/')
             name.append('/');
     } else {
-        name.append('/');
-        name.append(service_name);
+        name.append(Instance::NamePrefix("/"));
         name.append('-');
     }
 

src/tests/Stub.am

@@ -22,6 +22,7 @@ STUB_SOURCE = \
 	tests/stub_HttpReply.cc \
 	tests/stub_HttpRequest.cc \
 	tests/stub_HttpUpgradeProtocolAccess.cc \
+	tests/stub_Instance.cc \
 	tests/stub_IpcIoFile.cc \
 	tests/stub_MemBuf.cc \
 	tests/stub_MemObject.cc \

src/tests/stub_Instance.cc

@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 1996-2025 The Squid Software Foundation and contributors
+ *
+ * Squid software is distributed under GPLv2+ license and includes
+ * contributions from numerous individuals and organizations.
+ * Please see the COPYING and CONTRIBUTORS files for details.
+ */
+
+#include "squid.h"
+#include "Instance.h"
+#include "sbuf/SBuf.h"
+
+#define STUB_API "Instance.cc"
+#include "tests/STUB.h"
+
+void Instance::ThrowIfAlreadyRunning() STUB
+void Instance::WriteOurPid() STUB
+pid_t Instance::Other() STUB_RETVAL({})
+SBuf Instance::NamePrefix(const char *, const char *) STUB_RETVAL_NOP(SBuf("squid-STUB-0000"))
+