feat: resolve real Docker container names in CONTAINER column

Makefile.am

@@ -189,6 +189,7 @@ linux_platform_headers = \
 	generic/hostname.h \
 	generic/uname.h \
 	linux/CGroupUtils.h \
+	linux/DockerMgr.h \
 	linux/Compat.h \
 	linux/GPU.h \
 	linux/HugePageMeter.h \
@@ -218,6 +219,7 @@ linux_platform_sources = \
 	generic/hostname.c \
 	generic/uname.c \
 	linux/CGroupUtils.c \
+	linux/DockerMgr.c \
 	linux/Compat.c \
 	linux/GPU.c \
 	linux/HugePageMeter.c \

linux/CGroupUtils.c

@@ -515,7 +515,7 @@ char* CGroup_filterContainer(const char* cgroup) {
    }
 
    if (!s.pos) {
-      return xStrdup("/");
+      return xStrdup("");
    }
 
    s.buf = xCalloc(s.pos + 1, sizeof(char));

linux/DockerMgr.c

@@ -0,0 +1,108 @@
+/*
+htop - DockerMgr.c
+Retrieves running Docker container names via the Docker API over the unix socket.
+Released under the GNU GPLv2+, see the COPYING file
+in the source distribution for its full text.
+*/
+
+#include "config.h" // IWYU pragma: keep
+
+#include "linux/DockerMgr.h"
+
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include "Hashtable.h"
+#include "XUtils.h"
+
+#define DOCKER_SOCKET "/var/run/docker.sock"
+#define RESPONSE_SIZE 262144
+#define MAX_CONTAINER_NAME_LEN 25
+
+/* ponytail: simplest possible cache; refresh by dropping cache on long IDs is out of scope */
+static Hashtable* nameCache = NULL;
+
+static unsigned int hashStr(const char* s) {
+   unsigned int h = 5381;
+   while (*s)
+      h = (h * 33) ^ (unsigned char)*s++;
+   return h;
+}
+
+static Hashtable* getCache(void) {
+   if (!nameCache)
+      nameCache = Hashtable_new(16, true);
+   return nameCache;
+}
+
+static char* queryName(const char* id) {
+   int fd = socket(AF_UNIX, SOCK_STREAM, 0);
+   if (fd < 0)
+      return NULL;
+
+   struct sockaddr_un addr;
+   memset(&addr, 0, sizeof(addr));
+   addr.sun_family = AF_UNIX;
+   snprintf(addr.sun_path, sizeof(addr.sun_path), "%s", DOCKER_SOCKET);
+
+   if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
+      close(fd);
+      return NULL;
+   }
+
+   char req[256];
+   int reqLen = snprintf(req, sizeof(req),
+      "GET /containers/%s/json HTTP/1.1\r\n"
+      "Host: localhost\r\n"
+      "Accept: application/json\r\n"
+      "Connection: close\r\n\r\n", id);
+   if (reqLen <= 0 || reqLen >= (int)sizeof(req) || write(fd, req, (size_t)reqLen) != reqLen) {
+      close(fd);
+      return NULL;
+   }
+
+   char buf[RESPONSE_SIZE];
+   size_t used = 0;
+   ssize_t rd;
+   while (used < sizeof(buf) - 1 && (rd = read(fd, buf + used, sizeof(buf) - 1 - used)) > 0)
+      used += (size_t)rd;
+   close(fd);
+
+   if (used == 0)
+      return NULL;
+   buf[used] = '\0';
+
+   char* key = strstr(buf, "\"Name\":\"");
+   if (!key)
+      return NULL;
+   char* val = key + strlen("\"Name\":\"");
+   if (*val == '/')
+      val++;
+   char* end = strchr(val, '"');
+   if (!end)
+      return NULL;
+   return xStrndup(val, (size_t)(end - val));
+}
+
+char* DockerMgr_getContainerName(const char* id) {
+   Hashtable* cache = getCache();
+   ht_key_t key = hashStr(id);
+
+   char* cached = Hashtable_get(cache, key);
+   if (cached)
+      return xStrdup(cached);
+
+   char* name = queryName(id);
+   if (name) {
+      /* Limit the container name shown in the CONTAINER column to 25 characters */
+      char* shortName = xStrndup(name, MAX_CONTAINER_NAME_LEN);
+      free(name);
+      Hashtable_put(cache, key, shortName);
+      return xStrdup(shortName);
+   }
+   return NULL;
+}

linux/DockerMgr.h

@@ -0,0 +1,12 @@
+#ifndef HEADER_DockerMgr
+#define HEADER_DockerMgr
+/*
+htop - DockerMgr.h
+Retrieves running Docker container names via the Docker API over the unix socket.
+Released under the GNU GPLv2+, see the COPYING file
+in the source distribution for its full text.
+*/
+
+char* DockerMgr_getContainerName(const char* id);
+
+#endif /* HEADER_DockerMgr */

linux/LinuxProcessTable.c

@@ -40,6 +40,7 @@ in the source distribution for its full text.
 #include "Table.h"
 #include "UsersTable.h"
 #include "linux/CGroupUtils.h"
+#include "linux/DockerMgr.h"
 #include "linux/Compat.h"
 #include "linux/GPU.h"
 #include "linux/LinuxMachine.h"
@@ -1005,6 +1006,15 @@ static void LinuxProcessTable_readCGroupFile(LinuxProcess* process, openat_arg_t
 
    char* container_short = CGroup_filterContainer(process->cgroup);
    if (container_short) {
+      /* If this is a Docker container, try to resolve the real name via the Docker API */
+      static const char* dockerPrefix = "!docker:";
+      if (String_startsWith(container_short, dockerPrefix)) {
+         char* resolved = DockerMgr_getContainerName(container_short + strlen(dockerPrefix));
+         if (resolved) {
+            free(container_short);
+            container_short = resolved;
+         }
+      }
       Row_updateFieldWidth(CONTAINER, strlen(container_short));
       free_and_xStrdup(&process->container_short, container_short);
       free(container_short);