Merge branch 'net-reduce-sk_filter-and-friends-bloat'

Eric Dumazet says:

====================
net: reduce sk_filter() (and friends) bloat

Some functions return an error by value, and a drop_reason
by an output parameter. This extra parameter can force stack canaries.

A drop_reason is enough and more efficient.

This series reduces bloat by 678 bytes on x86_64:

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.final
add/remove: 0/0 grow/shrink: 3/18 up/down: 79/-757 (-678)
Function                                     old     new   delta
vsock_queue_rcv_skb                           50      79     +29
ipmr_cache_report                           1290    1315     +25
ip6mr_cache_report                          1322    1347     +25
tcp_v6_rcv                                  3169    3167      -2
packet_rcv_spkt                              329     327      -2
unix_dgram_sendmsg                          1731    1726      -5
netlink_unicast                              957     945     -12
netlink_dump                                1372    1359     -13
sk_filter_trim_cap                           889     858     -31
netlink_broadcast_filtered                  1633    1595     -38
tcp_v4_rcv                                  3152    3111     -41
raw_rcv_skb                                  122      80     -42
ping_queue_rcv_skb                           109      61     -48
ping_rcv                                     215     162     -53
rawv6_rcv_skb                                278     224     -54
__sk_receive_skb                             690     632     -58
raw_rcv                                      591     527     -64
udpv6_queue_rcv_one_skb                      935     869     -66
udp_queue_rcv_one_skb                        919     853     -66
tun_net_xmit                                1146    1074     -72
sock_queue_rcv_skb_reason                    166      76     -90
Total: Before=29722890, After=29722212, chg -0.00%

Future conversions from sock_queue_rcv_skb() to sock_queue_rcv_skb_reason()
can be done later.
====================

Link: https://patch.msgid.link/20260409145625.2306224-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 25 insertions, 13 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 44d7ae95ddbc..5ac08aa70123 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1092,20 +1092,21 @@ bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
 	return set_memory_rox((unsigned long)hdr, hdr->size >> PAGE_SHIFT);
 }
 
-int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap,
-		       enum skb_drop_reason *reason);
+enum skb_drop_reason
+sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);
 
 static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
 {
-	enum skb_drop_reason ignore_reason;
+	enum skb_drop_reason drop_reason;
 
-	return sk_filter_trim_cap(sk, skb, 1, &ignore_reason);
+	drop_reason = sk_filter_trim_cap(sk, skb, 1);
+	return drop_reason ? -EPERM : 0;
 }
 
-static inline int sk_filter_reason(struct sock *sk, struct sk_buff *skb,
-				   enum skb_drop_reason *reason)
+static inline enum skb_drop_reason
+sk_filter_reason(struct sock *sk, struct sk_buff *skb)
 {
-	return sk_filter_trim_cap(sk, skb, 1, reason);
+	return sk_filter_trim_cap(sk, skb, 1);
 }
 
 struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err);
diff --git a/include/net/sock.h b/include/net/sock.h
index 7d51ac9e7d9a..5831a4d1ebe7 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2502,12 +2502,23 @@ int __sk_queue_drop_skb(struct sock *sk, struct sk_buff_head *sk_queue,
 					   struct sk_buff *skb));
 int __sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
 
-int sock_queue_rcv_skb_reason(struct sock *sk, struct sk_buff *skb,
-			      enum skb_drop_reason *reason);
+enum skb_drop_reason
+sock_queue_rcv_skb_reason(struct sock *sk, struct sk_buff *skb);
 
 static inline int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
-	return sock_queue_rcv_skb_reason(sk, skb, NULL);
+	enum skb_drop_reason drop_reason = sock_queue_rcv_skb_reason(sk, skb);
+
+	switch (drop_reason) {
+	case SKB_DROP_REASON_SOCKET_RCVBUFF:
+		return -ENOMEM;
+	case SKB_DROP_REASON_PROTO_MEM:
+		return -ENOBUFS;
+	case 0:
+		return 0;
+	default:
+		return -EPERM;
+	}
 }
 
 int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb);
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 23ce0329b230..0f09429ff4cb 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1682,12 +1682,12 @@ static inline bool tcp_checksum_complete(struct sk_buff *skb)
 
 enum skb_drop_reason tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
 
-static inline int tcp_filter(struct sock *sk, struct sk_buff *skb,
-			     enum skb_drop_reason *reason)
+static inline enum skb_drop_reason
+tcp_filter(struct sock *sk, struct sk_buff *skb)
 {
 	const struct tcphdr *th = (const struct tcphdr *)skb->data;
 
-	return sk_filter_trim_cap(sk, skb, __tcp_hdrlen(th), reason);
+	return sk_filter_trim_cap(sk, skb, __tcp_hdrlen(th));
 }
 
 void tcp_set_state(struct sock *sk, int state);