bpftool: Match programs by name

When working with frequently modified BPF programs, both the ID and the
tag may change.  bpftool currently doesn't provide a "stable" way to match
such programs.

This patch implements lookup by name for programs.  The show and dump
commands will return all programs with the given name, whereas other
commands will error out if several programs have the same name.

Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Link: https://lore.kernel.org/bpf/b5fc1a5dcfaeb5f16fc80295cdaa606dd2d91534.1576263640.git.paul.chaignon@gmail.com

1 files changed, 18 insertions, 4 deletions

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 37948c47aabd..2221bae037f1 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -82,7 +82,7 @@ static void print_boot_time(__u64 nsecs, char *buf, unsigned int size)
 		strftime(buf, size, "%FT%T%z", &load_tm);
 }
 
-static int prog_fd_by_tag(unsigned char *tag, int **fds)
+static int prog_fd_by_nametag(void *nametag, int **fds, bool tag)
 {
 	unsigned int id = 0;
 	int fd, nb_fds = 0;
@@ -116,7 +116,8 @@ static int prog_fd_by_tag(unsigned char *tag, int **fds)
 			goto err_close_fd;
 		}
 
-		if (memcmp(tag, info.tag, BPF_TAG_SIZE)) {
+		if ((tag && memcmp(nametag, info.tag, BPF_TAG_SIZE)) ||
+		    (!tag && strncmp(nametag, info.name, BPF_OBJ_NAME_LEN))) {
 			close(fd);
 			continue;
 		}
@@ -174,7 +175,20 @@ static int prog_parse_fds(int *argc, char ***argv, int **fds)
 		}
 		NEXT_ARGP();
 
-		return prog_fd_by_tag(tag, fds);
+		return prog_fd_by_nametag(tag, fds, true);
+	} else if (is_prefix(**argv, "name")) {
+		char *name;
+
+		NEXT_ARGP();
+
+		name = **argv;
+		if (strlen(name) > BPF_OBJ_NAME_LEN - 1) {
+			p_err("can't parse name");
+			return -1;
+		}
+		NEXT_ARGP();
+
+		return prog_fd_by_nametag(name, fds, false);
 	} else if (is_prefix(**argv, "pinned")) {
 		char *path;
 
@@ -189,7 +203,7 @@ static int prog_parse_fds(int *argc, char ***argv, int **fds)
 		return 1;
 	}
 
-	p_err("expected 'id', 'tag' or 'pinned', got: '%s'?", **argv);
+	p_err("expected 'id', 'tag', 'name' or 'pinned', got: '%s'?", **argv);
 	return -1;
 }