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tcp: change bpf_skops_hdr_opt_len() signature

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Some compilers do not inline bpf_skops_hdr_opt_len() from
tcp_established_options(), forcing an expensive stack canary
when CONFIG_STACKPROTECTOR_STRONG=y.

Change bpf_skops_hdr_opt_len() to return @remaining by value
to remove this stack canary from TCP fast path.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/0 grow/shrink: 1/1 up/down: 10/-59 (-49)
Function                                     old     new   delta
bpf_skops_hdr_opt_len                        297     307     +10
tcp_established_options                      574     515     -59
Total: Before=31456795, After=31456746, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260601093819.469626-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-06-01 09:38:19 +00:00 committed by Jakub Kicinski
parent c0b3005e32
commit ceac8dbce6
1 changed files with 27 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
net/ipv4/tcp_output.c
View File

@ -466,22 +466,22 @@ static int bpf_skops_write_hdr_opt_arg0(struct sk_buff *skb,
}
/* req, syn_skb and synack_type are used when writing synack */
static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct sk_buff *syn_skb,
enum tcp_synack_type synack_type,
struct tcp_out_options *opts,
unsigned int *remaining)
static u32 bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct sk_buff *syn_skb,
enum tcp_synack_type synack_type,
struct tcp_out_options *opts,
u32 remaining)
{
struct bpf_sock_ops_kern sock_ops;
int err;
if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) ||
!*remaining)
return;
!remaining)
return remaining;
/* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */
/* remaining has already been aligned to 4 bytes, so remaining >= 4 */
/* init sock_ops */
memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
@ -513,21 +513,21 @@ static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
}
sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
sock_ops.remaining_opt_len = *remaining;
sock_ops.remaining_opt_len = remaining;
/* tcp_current_mss() does not pass a skb */
if (skb)
bpf_skops_init_skb(&sock_ops, skb, 0);
err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
if (err || sock_ops.remaining_opt_len == *remaining)
return;
if (err || sock_ops.remaining_opt_len == remaining)
return remaining;
opts->bpf_opt_len = *remaining - sock_ops.remaining_opt_len;
opts->bpf_opt_len = remaining - sock_ops.remaining_opt_len;
/* round up to 4 bytes */
opts->bpf_opt_len = (opts->bpf_opt_len + 3) & ~3;
*remaining -= opts->bpf_opt_len;
return remaining - opts->bpf_opt_len;
}
static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
@ -575,13 +575,14 @@ static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
max_opt_len - nr_written);
}
#else
static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct sk_buff *syn_skb,
enum tcp_synack_type synack_type,
struct tcp_out_options *opts,
unsigned int *remaining)
static u32 bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct sk_buff *syn_skb,
enum tcp_synack_type synack_type,
struct tcp_out_options *opts,
u32 remaining)
{
return remaining;
}
static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
@ -1050,7 +1051,8 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
remaining -= tcp_options_fit_accecn(opts, 0, remaining);
}
bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
remaining = bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts,
remaining);
return MAX_TCP_OPTION_SPACE - remaining;
}
@ -1137,8 +1139,8 @@ static unsigned int tcp_synack_options(const struct sock *sk,
remaining -= tcp_options_fit_accecn(opts, 0, remaining);
}
bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb,
synack_type, opts, &remaining);
remaining = bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb,
synack_type, opts, remaining);
return MAX_TCP_OPTION_SPACE - remaining;
}
@ -1227,7 +1229,8 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) {
unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
remaining = bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts,
remaining);
size = MAX_TCP_OPTION_SPACE - remaining;
}