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-rw-r--r--net/ipv4/tcp_output.c329
1 files changed, 272 insertions, 57 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index fcd278a7080e..93316a96d820 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -59,6 +59,10 @@ int sysctl_tcp_base_mss __read_mostly = 512;
/* By default, RFC2861 behavior. */
int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
+int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */
+EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size);
+
+
/* Account for new data that has been sent to the network. */
static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
{
@@ -362,15 +366,45 @@ static inline int tcp_urg_mode(const struct tcp_sock *tp)
#define OPTION_TS (1 << 1)
#define OPTION_MD5 (1 << 2)
#define OPTION_WSCALE (1 << 3)
+#define OPTION_COOKIE_EXTENSION (1 << 4)
struct tcp_out_options {
u8 options; /* bit field of OPTION_* */
u8 ws; /* window scale, 0 to disable */
u8 num_sack_blocks; /* number of SACK blocks to include */
+ u8 hash_size; /* bytes in hash_location */
u16 mss; /* 0 to disable */
__u32 tsval, tsecr; /* need to include OPTION_TS */
+ __u8 *hash_location; /* temporary pointer, overloaded */
};
+/* The sysctl int routines are generic, so check consistency here.
+ */
+static u8 tcp_cookie_size_check(u8 desired)
+{
+ if (desired > 0) {
+ /* previously specified */
+ return desired;
+ }
+ if (sysctl_tcp_cookie_size <= 0) {
+ /* no default specified */
+ return 0;
+ }
+ if (sysctl_tcp_cookie_size <= TCP_COOKIE_MIN) {
+ /* value too small, specify minimum */
+ return TCP_COOKIE_MIN;
+ }
+ if (sysctl_tcp_cookie_size >= TCP_COOKIE_MAX) {
+ /* value too large, specify maximum */
+ return TCP_COOKIE_MAX;
+ }
+ if (0x1 & sysctl_tcp_cookie_size) {
+ /* 8-bit multiple, illegal, fix it */
+ return (u8)(sysctl_tcp_cookie_size + 0x1);
+ }
+ return (u8)sysctl_tcp_cookie_size;
+}
+
/* Write previously computed TCP options to the packet.
*
* Beware: Something in the Internet is very sensitive to the ordering of
@@ -385,17 +419,34 @@ struct tcp_out_options {
* (but it may well be that other scenarios fail similarly).
*/
static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
- const struct tcp_out_options *opts,
- __u8 **md5_hash) {
- if (unlikely(OPTION_MD5 & opts->options)) {
- *ptr++ = htonl((TCPOPT_NOP << 24) |
- (TCPOPT_NOP << 16) |
- (TCPOPT_MD5SIG << 8) |
- TCPOLEN_MD5SIG);
- *md5_hash = (__u8 *)ptr;
+ struct tcp_out_options *opts)
+{
+ u8 options = opts->options; /* mungable copy */
+
+ /* Having both authentication and cookies for security is redundant,
+ * and there's certainly not enough room. Instead, the cookie-less
+ * extension variant is proposed.
+ *
+ * Consider the pessimal case with authentication. The options
+ * could look like:
+ * COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40
+ */
+ if (unlikely(OPTION_MD5 & options)) {
+ if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
+ *ptr++ = htonl((TCPOPT_COOKIE << 24) |
+ (TCPOLEN_COOKIE_BASE << 16) |
+ (TCPOPT_MD5SIG << 8) |
+ TCPOLEN_MD5SIG);
+ } else {
+ *ptr++ = htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_NOP << 16) |
+ (TCPOPT_MD5SIG << 8) |
+ TCPOLEN_MD5SIG);
+ }
+ options &= ~OPTION_COOKIE_EXTENSION;
+ /* overload cookie hash location */
+ opts->hash_location = (__u8 *)ptr;
ptr += 4;
- } else {
- *md5_hash = NULL;
}
if (unlikely(opts->mss)) {
@@ -404,12 +455,13 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
opts->mss);
}
- if (likely(OPTION_TS & opts->options)) {
- if (unlikely(OPTION_SACK_ADVERTISE & opts->options)) {
+ if (likely(OPTION_TS & options)) {
+ if (unlikely(OPTION_SACK_ADVERTISE & options)) {
*ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
(TCPOLEN_SACK_PERM << 16) |
(TCPOPT_TIMESTAMP << 8) |
TCPOLEN_TIMESTAMP);
+ options &= ~OPTION_SACK_ADVERTISE;
} else {
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
@@ -420,15 +472,52 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
*ptr++ = htonl(opts->tsecr);
}
- if (unlikely(OPTION_SACK_ADVERTISE & opts->options &&
- !(OPTION_TS & opts->options))) {
+ /* Specification requires after timestamp, so do it now.
+ *
+ * Consider the pessimal case without authentication. The options
+ * could look like:
+ * MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40
+ */
+ if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
+ __u8 *cookie_copy = opts->hash_location;
+ u8 cookie_size = opts->hash_size;
+
+ /* 8-bit multiple handled in tcp_cookie_size_check() above,
+ * and elsewhere.
+ */
+ if (0x2 & cookie_size) {
+ __u8 *p = (__u8 *)ptr;
+
+ /* 16-bit multiple */
+ *p++ = TCPOPT_COOKIE;
+ *p++ = TCPOLEN_COOKIE_BASE + cookie_size;
+ *p++ = *cookie_copy++;
+ *p++ = *cookie_copy++;
+ ptr++;
+ cookie_size -= 2;
+ } else {
+ /* 32-bit multiple */
+ *ptr++ = htonl(((TCPOPT_NOP << 24) |
+ (TCPOPT_NOP << 16) |
+ (TCPOPT_COOKIE << 8) |
+ TCPOLEN_COOKIE_BASE) +
+ cookie_size);
+ }
+
+ if (cookie_size > 0) {
+ memcpy(ptr, cookie_copy, cookie_size);
+ ptr += (cookie_size / 4);
+ }
+ }
+
+ if (unlikely(OPTION_SACK_ADVERTISE & options)) {
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_NOP << 16) |
(TCPOPT_SACK_PERM << 8) |
TCPOLEN_SACK_PERM);
}
- if (unlikely(OPTION_WSCALE & opts->options)) {
+ if (unlikely(OPTION_WSCALE & options)) {
*ptr++ = htonl((TCPOPT_NOP << 24) |
(TCPOPT_WINDOW << 16) |
(TCPOLEN_WINDOW << 8) |
@@ -463,13 +552,18 @@ static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb,
struct tcp_out_options *opts,
struct tcp_md5sig_key **md5) {
struct tcp_sock *tp = tcp_sk(sk);
- unsigned size = 0;
+ struct tcp_cookie_values *cvp = tp->cookie_values;
+ struct dst_entry *dst = __sk_dst_get(sk);
+ unsigned remaining = MAX_TCP_OPTION_SPACE;
+ u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ?
+ tcp_cookie_size_check(cvp->cookie_desired) :
+ 0;
#ifdef CONFIG_TCP_MD5SIG
*md5 = tp->af_specific->md5_lookup(sk, sk);
if (*md5) {
opts->options |= OPTION_MD5;
- size += TCPOLEN_MD5SIG_ALIGNED;
+ remaining -= TCPOLEN_MD5SIG_ALIGNED;
}
#else
*md5 = NULL;
@@ -485,26 +579,76 @@ static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb,
* SACKs don't matter, we never delay an ACK when we have any of those
* going out. */
opts->mss = tcp_advertise_mss(sk);
- size += TCPOLEN_MSS_ALIGNED;
+ remaining -= TCPOLEN_MSS_ALIGNED;
- if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
+ if (likely(sysctl_tcp_timestamps &&
+ !dst_feature(dst, RTAX_FEATURE_NO_TSTAMP) &&
+ *md5 == NULL)) {
opts->options |= OPTION_TS;
opts->tsval = TCP_SKB_CB(skb)->when;
opts->tsecr = tp->rx_opt.ts_recent;
- size += TCPOLEN_TSTAMP_ALIGNED;
+ remaining -= TCPOLEN_TSTAMP_ALIGNED;
}
- if (likely(sysctl_tcp_window_scaling)) {
+ if (likely(sysctl_tcp_window_scaling &&
+ !dst_feature(dst, RTAX_FEATURE_NO_WSCALE))) {
opts->ws = tp->rx_opt.rcv_wscale;
opts->options |= OPTION_WSCALE;
- size += TCPOLEN_WSCALE_ALIGNED;
+ remaining -= TCPOLEN_WSCALE_ALIGNED;
}
- if (likely(sysctl_tcp_sack)) {
+ if (likely(sysctl_tcp_sack &&
+ !dst_feature(dst, RTAX_FEATURE_NO_SACK))) {
opts->options |= OPTION_SACK_ADVERTISE;
if (unlikely(!(OPTION_TS & opts->options)))
- size += TCPOLEN_SACKPERM_ALIGNED;
+ remaining -= TCPOLEN_SACKPERM_ALIGNED;
}
- return size;
+ /* Note that timestamps are required by the specification.
+ *
+ * Odd numbers of bytes are prohibited by the specification, ensuring
+ * that the cookie is 16-bit aligned, and the resulting cookie pair is
+ * 32-bit aligned.
+ */
+ if (*md5 == NULL &&
+ (OPTION_TS & opts->options) &&
+ cookie_size > 0) {
+ int need = TCPOLEN_COOKIE_BASE + cookie_size;
+
+ if (0x2 & need) {
+ /* 32-bit multiple */
+ need += 2; /* NOPs */
+
+ if (need > remaining) {
+ /* try shrinking cookie to fit */
+ cookie_size -= 2;
+ need -= 4;
+ }
+ }
+ while (need > remaining && TCP_COOKIE_MIN <= cookie_size) {
+ cookie_size -= 4;
+ need -= 4;
+ }
+ if (TCP_COOKIE_MIN <= cookie_size) {
+ opts->options |= OPTION_COOKIE_EXTENSION;
+ opts->hash_location = (__u8 *)&cvp->cookie_pair[0];
+ opts->hash_size = cookie_size;
+
+ /* Remember for future incarnations. */
+ cvp->cookie_desired = cookie_size;
+
+ if (cvp->cookie_desired != cvp->cookie_pair_size) {
+ /* Currently use random bytes as a nonce,
+ * assuming these are completely unpredictable
+ * by hostile users of the same system.
+ */
+ get_random_bytes(&cvp->cookie_pair[0],
+ cookie_size);
+ cvp->cookie_pair_size = cookie_size;
+ }
+
+ remaining -= need;
+ }
+ }
+ return MAX_TCP_OPTION_SPACE - remaining;
}
/* Set up TCP options for SYN-ACKs. */
@@ -512,48 +656,77 @@ static unsigned tcp_synack_options(struct sock *sk,
struct request_sock *req,
unsigned mss, struct sk_buff *skb,
struct tcp_out_options *opts,
- struct tcp_md5sig_key **md5) {
- unsigned size = 0;
+ struct tcp_md5sig_key **md5,
+ struct tcp_extend_values *xvp)
+{
struct inet_request_sock *ireq = inet_rsk(req);
- char doing_ts;
+ unsigned remaining = MAX_TCP_OPTION_SPACE;
+ u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
+ xvp->cookie_plus :
+ 0;
+ bool doing_ts = ireq->tstamp_ok;
#ifdef CONFIG_TCP_MD5SIG
*md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
if (*md5) {
opts->options |= OPTION_MD5;
- size += TCPOLEN_MD5SIG_ALIGNED;
+ remaining -= TCPOLEN_MD5SIG_ALIGNED;
+
+ /* We can't fit any SACK blocks in a packet with MD5 + TS
+ * options. There was discussion about disabling SACK
+ * rather than TS in order to fit in better with old,
+ * buggy kernels, but that was deemed to be unnecessary.
+ */
+ doing_ts &= !ireq->sack_ok;
}
#else
*md5 = NULL;
#endif
- /* we can't fit any SACK blocks in a packet with MD5 + TS
- options. There was discussion about disabling SACK rather than TS in
- order to fit in better with old, buggy kernels, but that was deemed
- to be unnecessary. */
- doing_ts = ireq->tstamp_ok && !(*md5 && ireq->sack_ok);
-
+ /* We always send an MSS option. */
opts->mss = mss;
- size += TCPOLEN_MSS_ALIGNED;
+ remaining -= TCPOLEN_MSS_ALIGNED;
if (likely(ireq->wscale_ok)) {
opts->ws = ireq->rcv_wscale;
opts->options |= OPTION_WSCALE;
- size += TCPOLEN_WSCALE_ALIGNED;
+ remaining -= TCPOLEN_WSCALE_ALIGNED;
}
if (likely(doing_ts)) {
opts->options |= OPTION_TS;
opts->tsval = TCP_SKB_CB(skb)->when;
opts->tsecr = req->ts_recent;
- size += TCPOLEN_TSTAMP_ALIGNED;
+ remaining -= TCPOLEN_TSTAMP_ALIGNED;
}
if (likely(ireq->sack_ok)) {
opts->options |= OPTION_SACK_ADVERTISE;
if (unlikely(!doing_ts))
- size += TCPOLEN_SACKPERM_ALIGNED;
+ remaining -= TCPOLEN_SACKPERM_ALIGNED;
}
- return size;
+ /* Similar rationale to tcp_syn_options() applies here, too.
+ * If the <SYN> options fit, the same options should fit now!
+ */
+ if (*md5 == NULL &&
+ doing_ts &&
+ cookie_plus > TCPOLEN_COOKIE_BASE) {
+ int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */
+
+ if (0x2 & need) {
+ /* 32-bit multiple */
+ need += 2; /* NOPs */
+ }
+ if (need <= remaining) {
+ opts->options |= OPTION_COOKIE_EXTENSION;
+ opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE;
+ remaining -= need;
+ } else {
+ /* There's no error return, so flag it. */
+ xvp->cookie_out_never = 1; /* true */
+ opts->hash_size = 0;
+ }
+ }
+ return MAX_TCP_OPTION_SPACE - remaining;
}
/* Compute TCP options for ESTABLISHED sockets. This is not the
@@ -619,7 +792,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
struct tcp_out_options opts;
unsigned tcp_options_size, tcp_header_size;
struct tcp_md5sig_key *md5;
- __u8 *md5_hash_location;
struct tcphdr *th;
int err;
@@ -661,8 +833,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
/* Build TCP header and checksum it. */
th = tcp_hdr(skb);
- th->source = inet->sport;
- th->dest = inet->dport;
+ th->source = inet->inet_sport;
+ th->dest = inet->inet_dport;
th->seq = htonl(tcb->seq);
th->ack_seq = htonl(tp->rcv_nxt);
*(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
@@ -690,7 +862,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
}
}
- tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location);
+ tcp_options_write((__be32 *)(th + 1), tp, &opts);
if (likely((tcb->flags & TCPCB_FLAG_SYN) == 0))
TCP_ECN_send(sk, skb, tcp_header_size);
@@ -698,7 +870,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
/* Calculate the MD5 hash, as we have all we need now */
if (md5) {
sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
- tp->af_specific->calc_md5_hash(md5_hash_location,
+ tp->af_specific->calc_md5_hash(opts.hash_location,
md5, sk, NULL, skb);
}
#endif
@@ -1918,8 +2090,8 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
* case, when window is shrunk to zero. In this case
* our retransmit serves as a zero window probe.
*/
- if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))
- && TCP_SKB_CB(skb)->seq != tp->snd_una)
+ if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
+ TCP_SKB_CB(skb)->seq != tp->snd_una)
return -EAGAIN;
if (skb->len > cur_mss) {
@@ -2219,16 +2391,17 @@ int tcp_send_synack(struct sock *sk)
/* Prepare a SYN-ACK. */
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
- struct request_sock *req)
+ struct request_sock *req,
+ struct request_values *rvp)
{
+ struct tcp_out_options opts;
+ struct tcp_extend_values *xvp = tcp_xv(rvp);
struct inet_request_sock *ireq = inet_rsk(req);
struct tcp_sock *tp = tcp_sk(sk);
struct tcphdr *th;
- int tcp_header_size;
- struct tcp_out_options opts;
struct sk_buff *skb;
struct tcp_md5sig_key *md5;
- __u8 *md5_hash_location;
+ int tcp_header_size;
int mss;
skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
@@ -2266,8 +2439,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
#endif
TCP_SKB_CB(skb)->when = tcp_time_stamp;
tcp_header_size = tcp_synack_options(sk, req, mss,
- skb, &opts, &md5) +
- sizeof(struct tcphdr);
+ skb, &opts, &md5, xvp)
+ + sizeof(*th);
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);
@@ -2284,19 +2457,58 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
*/
tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
TCPCB_FLAG_SYN | TCPCB_FLAG_ACK);
+
+ if (OPTION_COOKIE_EXTENSION & opts.options) {
+ const struct tcp_cookie_values *cvp = tp->cookie_values;
+
+ if (cvp != NULL &&
+ cvp->s_data_constant &&
+ cvp->s_data_desired > 0) {
+ u8 *buf = skb_put(skb, cvp->s_data_desired);
+
+ /* copy data directly from the listening socket. */
+ memcpy(buf, cvp->s_data_payload, cvp->s_data_desired);
+ TCP_SKB_CB(skb)->end_seq += cvp->s_data_desired;
+ }
+
+ if (opts.hash_size > 0) {
+ __u32 workspace[SHA_WORKSPACE_WORDS];
+ u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS];
+ u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1];
+
+ /* Secret recipe depends on the Timestamp, (future)
+ * Sequence and Acknowledgment Numbers, Initiator
+ * Cookie, and others handled by IP variant caller.
+ */
+ *tail-- ^= opts.tsval;
+ *tail-- ^= tcp_rsk(req)->rcv_isn + 1;
+ *tail-- ^= TCP_SKB_CB(skb)->seq + 1;
+
+ /* recommended */
+ *tail-- ^= ((th->dest << 16) | th->source);
+ *tail-- ^= (u32)(unsigned long)cvp; /* per sockopt */
+
+ sha_transform((__u32 *)&xvp->cookie_bakery[0],
+ (char *)mess,
+ &workspace[0]);
+ opts.hash_location =
+ (__u8 *)&xvp->cookie_bakery[0];
+ }
+ }
+
th->seq = htonl(TCP_SKB_CB(skb)->seq);
th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
th->window = htons(min(req->rcv_wnd, 65535U));
- tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location);
+ tcp_options_write((__be32 *)(th + 1), tp, &opts);
th->doff = (tcp_header_size >> 2);
TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
#ifdef CONFIG_TCP_MD5SIG
/* Okay, we have all we need - do the md5 hash if needed */
if (md5) {
- tcp_rsk(req)->af_specific->calc_md5_hash(md5_hash_location,
+ tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
md5, NULL, req, skb);
}
#endif
@@ -2315,7 +2527,9 @@ static void tcp_connect_init(struct sock *sk)
* See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
*/
tp->tcp_header_len = sizeof(struct tcphdr) +
- (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
+ (sysctl_tcp_timestamps &&
+ (!dst_feature(dst, RTAX_FEATURE_NO_TSTAMP) ?
+ TCPOLEN_TSTAMP_ALIGNED : 0));
#ifdef CONFIG_TCP_MD5SIG
if (tp->af_specific->md5_lookup(sk, sk) != NULL)
@@ -2341,7 +2555,8 @@ static void tcp_connect_init(struct sock *sk)
tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
&tp->rcv_wnd,
&tp->window_clamp,
- sysctl_tcp_window_scaling,
+ (sysctl_tcp_window_scaling &&
+ !dst_feature(dst, RTAX_FEATURE_NO_WSCALE)),
&rcv_wscale);
tp->rx_opt.rcv_wscale = rcv_wscale;
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.