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Diffstat (limited to 'net/ipv4/tcp_output.c')
-rw-r--r--net/ipv4/tcp_output.c165
1 files changed, 160 insertions, 5 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 5be2b3eb73d3..34e5c83bbace 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -385,6 +385,7 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)
#define OPTION_SMC BIT(9)
#define OPTION_MPTCP BIT(10)
#define OPTION_AO BIT(11)
+#define OPTION_ACCECN BIT(12)
static void smc_options_write(__be32 *ptr, u16 *options)
{
@@ -406,6 +407,8 @@ struct tcp_out_options {
u16 mss; /* 0 to disable */
u8 ws; /* window scale, 0 to disable */
u8 num_sack_blocks; /* number of SACK blocks to include */
+ u8 num_accecn_fields:7, /* number of AccECN fields needed */
+ use_synack_ecn_bytes:1; /* Use synack_ecn_bytes or not */
u8 hash_size; /* bytes in hash_location */
u8 bpf_opt_len; /* length of BPF hdr option */
__u8 *hash_location; /* temporary pointer, overloaded */
@@ -603,6 +606,11 @@ static __be32 *process_tcp_ao_options(struct tcp_sock *tp,
return ptr;
}
+/* Initial values for AccECN option, ordered is based on ECN field bits
+ * similar to received_ecn_bytes. Used for SYN/ACK AccECN option.
+ */
+static const u32 synack_ecn_bytes[3] = { 0, 0, 0 };
+
/* Write previously computed TCP options to the packet.
*
* Beware: Something in the Internet is very sensitive to the ordering of
@@ -621,6 +629,8 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
struct tcp_out_options *opts,
struct tcp_key *key)
{
+ u8 leftover_highbyte = TCPOPT_NOP; /* replace 1st NOP if avail */
+ u8 leftover_lowbyte = TCPOPT_NOP; /* replace 2nd NOP in succession */
__be32 *ptr = (__be32 *)(th + 1);
u16 options = opts->options; /* mungable copy */
@@ -656,15 +666,71 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
*ptr++ = htonl(opts->tsecr);
}
+ if (OPTION_ACCECN & options) {
+ const u32 *ecn_bytes = opts->use_synack_ecn_bytes ?
+ synack_ecn_bytes :
+ tp->received_ecn_bytes;
+ const u8 ect0_idx = INET_ECN_ECT_0 - 1;
+ const u8 ect1_idx = INET_ECN_ECT_1 - 1;
+ const u8 ce_idx = INET_ECN_CE - 1;
+ u32 e0b;
+ u32 e1b;
+ u32 ceb;
+ u8 len;
+
+ e0b = ecn_bytes[ect0_idx] + TCP_ACCECN_E0B_INIT_OFFSET;
+ e1b = ecn_bytes[ect1_idx] + TCP_ACCECN_E1B_INIT_OFFSET;
+ ceb = ecn_bytes[ce_idx] + TCP_ACCECN_CEB_INIT_OFFSET;
+ len = TCPOLEN_ACCECN_BASE +
+ opts->num_accecn_fields * TCPOLEN_ACCECN_PERFIELD;
+
+ if (opts->num_accecn_fields == 2) {
+ *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) |
+ ((e1b >> 8) & 0xffff));
+ *ptr++ = htonl(((e1b & 0xff) << 24) |
+ (ceb & 0xffffff));
+ } else if (opts->num_accecn_fields == 1) {
+ *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) |
+ ((e1b >> 8) & 0xffff));
+ leftover_highbyte = e1b & 0xff;
+ leftover_lowbyte = TCPOPT_NOP;
+ } else if (opts->num_accecn_fields == 0) {
+ leftover_highbyte = TCPOPT_ACCECN1;
+ leftover_lowbyte = len;
+ } else if (opts->num_accecn_fields == 3) {
+ *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) |
+ ((e1b >> 8) & 0xffff));
+ *ptr++ = htonl(((e1b & 0xff) << 24) |
+ (ceb & 0xffffff));
+ *ptr++ = htonl(((e0b & 0xffffff) << 8) |
+ TCPOPT_NOP);
+ }
+ if (tp)
+ tp->accecn_minlen = 0;
+ }
+
if (unlikely(OPTION_SACK_ADVERTISE & options)) {
- *ptr++ = htonl((TCPOPT_NOP << 24) |
- (TCPOPT_NOP << 16) |
+ *ptr++ = htonl((leftover_highbyte << 24) |
+ (leftover_lowbyte << 16) |
(TCPOPT_SACK_PERM << 8) |
TCPOLEN_SACK_PERM);
+ leftover_highbyte = TCPOPT_NOP;
+ leftover_lowbyte = TCPOPT_NOP;
}
if (unlikely(OPTION_WSCALE & options)) {
- *ptr++ = htonl((TCPOPT_NOP << 24) |
+ u8 highbyte = TCPOPT_NOP;
+
+ /* Do not split the leftover 2-byte to fit into a single
+ * NOP, i.e., replace this NOP only when 1 byte is leftover
+ * within leftover_highbyte.
+ */
+ if (unlikely(leftover_highbyte != TCPOPT_NOP &&
+ leftover_lowbyte == TCPOPT_NOP)) {
+ highbyte = leftover_highbyte;
+ leftover_highbyte = TCPOPT_NOP;
+ }
+ *ptr++ = htonl((highbyte << 24) |
(TCPOPT_WINDOW << 16) |
(TCPOLEN_WINDOW << 8) |
opts->ws);
@@ -675,11 +741,13 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
tp->duplicate_sack : tp->selective_acks;
int this_sack;
- *ptr++ = htonl((TCPOPT_NOP << 24) |
- (TCPOPT_NOP << 16) |
+ *ptr++ = htonl((leftover_highbyte << 24) |
+ (leftover_lowbyte << 16) |
(TCPOPT_SACK << 8) |
(TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
TCPOLEN_SACK_PERBLOCK)));
+ leftover_highbyte = TCPOPT_NOP;
+ leftover_lowbyte = TCPOPT_NOP;
for (this_sack = 0; this_sack < opts->num_sack_blocks;
++this_sack) {
@@ -688,6 +756,14 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
}
tp->rx_opt.dsack = 0;
+ } else if (unlikely(leftover_highbyte != TCPOPT_NOP ||
+ leftover_lowbyte != TCPOPT_NOP)) {
+ *ptr++ = htonl((leftover_highbyte << 24) |
+ (leftover_lowbyte << 16) |
+ (TCPOPT_NOP << 8) |
+ TCPOPT_NOP);
+ leftover_highbyte = TCPOPT_NOP;
+ leftover_lowbyte = TCPOPT_NOP;
}
if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
@@ -768,6 +844,61 @@ static void mptcp_set_option_cond(const struct request_sock *req,
}
}
+static u32 tcp_synack_options_combine_saving(struct tcp_out_options *opts)
+{
+ /* How much there's room for combining with the alignment padding? */
+ if ((opts->options & (OPTION_SACK_ADVERTISE | OPTION_TS)) ==
+ OPTION_SACK_ADVERTISE)
+ return 2;
+ else if (opts->options & OPTION_WSCALE)
+ return 1;
+ return 0;
+}
+
+/* Calculates how long AccECN option will fit to @remaining option space.
+ *
+ * AccECN option can sometimes replace NOPs used for alignment of other
+ * TCP options (up to @max_combine_saving available).
+ *
+ * Only solutions with at least @required AccECN fields are accepted.
+ *
+ * Returns: The size of the AccECN option excluding space repurposed from
+ * the alignment of the other options.
+ */
+static int tcp_options_fit_accecn(struct tcp_out_options *opts, int required,
+ int remaining)
+{
+ int size = TCP_ACCECN_MAXSIZE;
+ int max_combine_saving;
+ int align_size;
+
+ if (opts->use_synack_ecn_bytes)
+ max_combine_saving = tcp_synack_options_combine_saving(opts);
+ else
+ max_combine_saving = opts->num_sack_blocks > 0 ? 2 : 0;
+ opts->num_accecn_fields = TCP_ACCECN_NUMFIELDS;
+ while (opts->num_accecn_fields >= required) {
+ /* Pad to dword if cannot combine */
+ if ((size & 0x3) > max_combine_saving)
+ align_size = ALIGN(size, 4);
+ else
+ align_size = ALIGN_DOWN(size, 4);
+
+ if (remaining >= align_size) {
+ size = align_size;
+ break;
+ }
+
+ opts->num_accecn_fields--;
+ size -= TCPOLEN_ACCECN_PERFIELD;
+ }
+ if (opts->num_accecn_fields < required)
+ return 0;
+
+ opts->options |= OPTION_ACCECN;
+ return size;
+}
+
/* Compute TCP options for SYN packets. This is not the final
* network wire format yet.
*/
@@ -850,6 +981,15 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
}
}
+ /* Simultaneous open SYN/ACK needs AccECN option but not SYN */
+ if (unlikely((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) &&
+ tcp_ecn_mode_accecn(tp) &&
+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) &&
+ remaining >= TCPOLEN_ACCECN_BASE)) {
+ opts->use_synack_ecn_bytes = 1;
+ remaining -= tcp_options_fit_accecn(opts, 0, remaining);
+ }
+
bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
return MAX_TCP_OPTION_SPACE - remaining;
@@ -867,6 +1007,7 @@ static unsigned int tcp_synack_options(const struct sock *sk,
{
struct inet_request_sock *ireq = inet_rsk(req);
unsigned int remaining = MAX_TCP_OPTION_SPACE;
+ struct tcp_request_sock *treq = tcp_rsk(req);
if (tcp_key_is_md5(key)) {
opts->options |= OPTION_MD5;
@@ -929,6 +1070,13 @@ static unsigned int tcp_synack_options(const struct sock *sk,
smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
+ if (treq->accecn_ok &&
+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) &&
+ remaining >= TCPOLEN_ACCECN_BASE) {
+ opts->use_synack_ecn_bytes = 1;
+ remaining -= tcp_options_fit_accecn(opts, 0, remaining);
+ }
+
bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb,
synack_type, opts, &remaining);
@@ -1001,6 +1149,13 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
opts->num_sack_blocks = 0;
}
+ if (tcp_ecn_mode_accecn(tp) &&
+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option)) {
+ opts->use_synack_ecn_bytes = 0;
+ size += tcp_options_fit_accecn(opts, tp->accecn_minlen,
+ MAX_TCP_OPTION_SPACE - size);
+ }
+
if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp,
BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) {
unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
generated by cgit v1.2.3 (git 2.46.0) at 2025-12-10 09:33:18 +0000