selftests/bpf: Replace TCP CC string comparisons with bpf_strncmp

The connect4_prog and bpf_iter_setsockopt tests duplicate the same
open-coded TCP congestion control string comparison logic. Since
bpf_strncmp() provides the same functionality, use it instead to
avoid repeated open-coded loops.

This change applies only to functional BPF tests and does not affect
the verifier performance benchmarks (veristat.cfg). No functional
changes intended.

Reviewed-by: Amery Hung <[email protected]>
Signed-off-by: Hoyeon Lee <[email protected]>
Signed-off-by: Martin KaFai Lau <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: HoyeonRhee

tools/testing/selftests/bpf/progs/bpf_iter_setsockopt.c

@@ -18,23 +18,10 @@
 
 unsigned short reuse_listen_hport = 0;
 unsigned short listen_hport = 0;
-char cubic_cc[TCP_CA_NAME_MAX] = "bpf_cubic";
+const char cubic_cc[] = "bpf_cubic";
 char dctcp_cc[TCP_CA_NAME_MAX] = "bpf_dctcp";
 bool random_retry = false;
 
-static bool tcp_cc_eq(const char *a, const char *b)
-{
-	int i;
-
-	for (i = 0; i < TCP_CA_NAME_MAX; i++) {
-		if (a[i] != b[i])
-			return false;
-		if (!a[i])
-			break;
-	}
-
-	return true;
-}
 
 SEC("iter/tcp")
 int change_tcp_cc(struct bpf_iter__tcp *ctx)
@@ -58,7 +45,7 @@ int change_tcp_cc(struct bpf_iter__tcp *ctx)
 			   cur_cc, sizeof(cur_cc)))
 		return 0;
 
-	if (!tcp_cc_eq(cur_cc, cubic_cc))
+	if (bpf_strncmp(cur_cc, TCP_CA_NAME_MAX, cubic_cc))
 		return 0;
 
 	if (random_retry && bpf_get_prandom_u32() % 4 == 1)

tools/testing/selftests/bpf/progs/connect4_prog.c

@@ -34,6 +34,9 @@
 #define SOL_TCP 6
 #endif
 
+const char reno[] = "reno";
+const char cubic[] = "cubic";
+
 __attribute__ ((noinline)) __weak
 int do_bind(struct bpf_sock_addr *ctx)
 {
@@ -50,35 +53,27 @@ int do_bind(struct bpf_sock_addr *ctx)
 }
 
 static __inline int verify_cc(struct bpf_sock_addr *ctx,
-			      char expected[TCP_CA_NAME_MAX])
+			      const char expected[])
 {
 	char buf[TCP_CA_NAME_MAX];
-	int i;
 
 	if (bpf_getsockopt(ctx, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
 		return 1;
 
-	for (i = 0; i < TCP_CA_NAME_MAX; i++) {
-		if (buf[i] != expected[i])
-			return 1;
-		if (buf[i] == 0)
-			break;
-	}
+	if (bpf_strncmp(buf, TCP_CA_NAME_MAX, expected))
+		return 1;
 
 	return 0;
 }
 
 static __inline int set_cc(struct bpf_sock_addr *ctx)
 {
-	char reno[TCP_CA_NAME_MAX] = "reno";
-	char cubic[TCP_CA_NAME_MAX] = "cubic";
-
-	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &reno, sizeof(reno)))
+	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, (void *)reno, sizeof(reno)))
 		return 1;
 	if (verify_cc(ctx, reno))
 		return 1;
 
-	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &cubic, sizeof(cubic)))
+	if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, (void *)cubic, sizeof(cubic)))
 		return 1;
 	if (verify_cc(ctx, cubic))
 		return 1;