From 0cfe3653d875afc0508333f444944ebb965ba300 Mon Sep 17 00:00:00 2001
From: Jiping Yin <jiping@yunshan.net>
Date: Sat, 12 Oct 2024 11:01:04 +0800
Subject: [PATCH] fix: agent - eBPF Handle the scenario where CONFIG_NET_NS is
 disabled (#8282)

Fix issues in certain custom kernel systems where the lack of the 'CONFIG_NET_NS' compile option causes process information to fail during the agent initialization phase.

Conflicts:
	agent/src/ebpf/user/tracer.c
---
 agent/src/ebpf/user/common.c | 25 +++++++++++++++++++++++--
 agent/src/ebpf/user/common.h |  1 +
 agent/src/ebpf/user/proc.c   |  2 --
 agent/src/ebpf/user/tracer.c |  5 +++++
 4 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/agent/src/ebpf/user/common.c b/agent/src/ebpf/user/common.c
index 9f2fae9d3fa..11f470a13b5 100644
--- a/agent/src/ebpf/user/common.c
+++ b/agent/src/ebpf/user/common.c
@@ -537,12 +537,17 @@ u64 get_process_starttime_and_comm(pid_t pid, char *name_base, int len)
 	unsigned long long etime_ticks = 0;
 
 	snprintf(file, sizeof(file), "/proc/%d/stat", pid);
-	if (access(file, F_OK))
+	if (access(file, F_OK)) {
+		ebpf_warning("file %s is not exited\n", file);
 		return 0;
+	}
 
 	fd = open(file, O_RDONLY);
-	if (fd <= 2)
+	if (fd <= 2) {
+		ebpf_warning("open %s failed with %s(%d)\n", file,
+			     strerror(errno), errno);
 		return 0;
+	}
 
 	read(fd, buff, sizeof(buff));
 	close(fd);
@@ -551,6 +556,7 @@ u64 get_process_starttime_and_comm(pid_t pid, char *name_base, int len)
 	if (sscanf(buff, "%*s %ms %*s %*s %*s %*s %*s %*s %*s %*s %*s"
 		   " %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %llu ",
 		   &start, &etime_ticks) != 2) {
+		ebpf_warning("sscanf() failed. pid %d buff %s\n", pid, buff);
 		return 0;
 	}
 
@@ -911,6 +917,21 @@ u64 get_netns_id_from_pid(pid_t pid)
 	return strtoull(netns_id_str, NULL, 10);
 }
 
+bool check_netns_enabled(void)
+{
+	char netns_path[MAX_PATH_LENGTH];
+	snprintf(netns_path, sizeof(netns_path), "/proc/1/ns/net");
+
+	char target_path[MAX_PATH_LENGTH];
+	ssize_t len =
+	    readlink(netns_path, target_path, sizeof(target_path) - 1);
+	if (len == -1) {
+		return false;
+	}
+
+	return true;
+}
+	
 // Function to retrieve the host PID from the first line of /proc/pid/sched
 // The expected format is "java (1234, #threads: 12)"
 // where 1234 is the host PID (before Linux 4.1)
diff --git a/agent/src/ebpf/user/common.h b/agent/src/ebpf/user/common.h
index a4f756ce6f7..29a895f88fe 100644
--- a/agent/src/ebpf/user/common.h
+++ b/agent/src/ebpf/user/common.h
@@ -281,6 +281,7 @@ u64 get_process_starttime_and_comm(pid_t pid,
 				   int len);
 u32 legacy_fetch_log2_page_size(void);
 u64 get_netns_id_from_pid(pid_t pid);
+bool check_netns_enabled(void);
 int get_nspid(int pid);
 int get_target_uid_and_gid(int target_pid, int *uid, int *gid);
 int copy_file(const char *src_file, const char *dest_file);
diff --git a/agent/src/ebpf/user/proc.c b/agent/src/ebpf/user/proc.c
index 461ddc6b0ee..9ed0fa79cdb 100644
--- a/agent/src/ebpf/user/proc.c
+++ b/agent/src/ebpf/user/proc.c
@@ -538,8 +538,6 @@ static int config_symbolizer_proc_info(struct symbolizer_proc_info *p, int pid)
 	p->thread_names = NULL;
 	p->thread_names_lock = 0;
 	p->netns_id = get_netns_id_from_pid(pid);
-	if (p->netns_id == 0)
-		return ETR_INVAL;
 
 	fetch_container_id(pid, p->container_id, sizeof(p->container_id));
 
diff --git a/agent/src/ebpf/user/tracer.c b/agent/src/ebpf/user/tracer.c
index efc40999a6f..27d301a0c1c 100644
--- a/agent/src/ebpf/user/tracer.c
+++ b/agent/src/ebpf/user/tracer.c
@@ -2056,6 +2056,11 @@ int bpf_tracer_init(const char *log_file, bool is_stdout)
 
 	init_thread_ids();
 
+	if (!check_netns_enabled())
+		ebpf_warning("If the system has not enabled the 'CONFIG_NET_NS'"
+			     " option, the 'netns_id' for continuously profiling"
+			     " data will be 0.\n");
+
 	/*
 	 * Set up the lock now, so we can use it to make the first add
 	 * thread-safe for tracer alloc.