From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by passt.top (Postfix) with ESMTPS id 8E84B5A02DC for ; Tue, 14 May 2024 03:03:50 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202312; t=1715648622; bh=4TLbNmNH4zORDtJUJxRb0nrFnFBBiy5oR0w8keAO9xY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=f1sRsTXaH/bMxK8A2ztI/8fcp2P0R2gz8Jk0jomNjeouX1CIFP5wPYnrbwyj2sZJQ SmmygiL/GFqgFJyJvRMCizkyQIWABML/Xf376TRdOy+Q8Qwig2BMdjStIBO0q7fSys hiNcLGKA9aJ5QwLnoKhYltRyhgUiEwPfVge0UnMKVY7PNw401sTPn4FsNqE6jT8tYl J600OKCGphBxFy+DOpyEvdbYthhoY6E16GUlcYsWWLSFUOLi8TkVoaqBmEBudY4YEc Xn4+DXVOfJGw1xCW8ixsdKDvODU6JfvEHTf94kaHSAKffTV4624dYeGbhgv9A1ZSKm tL4am9866C+4Q== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4VddQk12FCz4x1Y; Tue, 14 May 2024 11:03:42 +1000 (AEST) From: David Gibson To: Stefano Brivio , passt-dev@passt.top Subject: [PATCH v5 14/19] tcp: Re-use flow hash for initial sequence number generation Date: Tue, 14 May 2024 11:03:32 +1000 Message-ID: <20240514010337.1104606-15-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20240514010337.1104606-1-david@gibson.dropbear.id.au> References: <20240514010337.1104606-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: YPS6Z3O5CMEPSV7ECW3WXK6CAT2EUBTM X-Message-ID-Hash: YPS6Z3O5CMEPSV7ECW3WXK6CAT2EUBTM X-MailFrom: dgibson@gandalf.ozlabs.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: David Gibson X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: We generate TCP initial sequence numbers, when we need them, from a hash of the source and destination addresses and ports, plus a timestamp. Moments later, we generate another hash of the same information plus some more to insert the connection into the flow hash table. With some tweaks to the flow_hash_insert() interface and changing the order we can re-use that hash table hash for the initial sequence number, rather than calculating another one. It won't generate identical results, but that doesn't matter as long as the sequence numbers are well scattered. Signed-off-by: David Gibson --- flow.c | 30 ++++++++++++++++++++++++------ flow.h | 2 +- tcp.c | 33 +++++++++++---------------------- 3 files changed, 36 insertions(+), 29 deletions(-) diff --git a/flow.c b/flow.c index 30a6904..4942075 100644 --- a/flow.c +++ b/flow.c @@ -451,16 +451,16 @@ static uint64_t flow_sidx_hash(const struct ctx *c, flow_sidx_t sidx) } /** - * flow_hash_probe() - Find hash bucket for a flow - * @c: Execution context + * flow_hash_probe_() - Find hash bucket for a flow, given hash + * @hash: Raw hash value for flow & side * @sidx: Flow and side to find bucket for * * Return: If @sidx is in the hash table, its current bucket, otherwise a * suitable free bucket for it. */ -static inline unsigned flow_hash_probe(const struct ctx *c, flow_sidx_t sidx) +static inline unsigned flow_hash_probe_(uint64_t hash, flow_sidx_t sidx) { - unsigned b = flow_sidx_hash(c, sidx) % FLOW_HASH_SIZE; + unsigned b = hash % FLOW_HASH_SIZE; /* Linear probing */ while (!flow_sidx_eq(flow_hashtab[b], FLOW_SIDX_NONE) && @@ -470,17 +470,35 @@ static inline unsigned flow_hash_probe(const struct ctx *c, flow_sidx_t sidx) return b; } +/** + * flow_hash_probe() - Find hash bucket for a flow + * @c: Execution context + * @sidx: Flow and side to find bucket for + * + * Return: If @sidx is in the hash table, its current bucket, otherwise a + * suitable free bucket for it. + */ +static inline unsigned flow_hash_probe(const struct ctx *c, flow_sidx_t sidx) +{ + return flow_hash_probe_(flow_sidx_hash(c, sidx), sidx); +} + /** * flow_hash_insert() - Insert side of a flow into into hash table * @c: Execution context * @sidx: Flow & side index + * + * Return: raw (un-modded) hash value of side of flow */ -void flow_hash_insert(const struct ctx *c, flow_sidx_t sidx) +uint64_t flow_hash_insert(const struct ctx *c, flow_sidx_t sidx) { - unsigned b = flow_hash_probe(c, sidx); + uint64_t hash = flow_sidx_hash(c, sidx); + unsigned b = flow_hash_probe_(hash, sidx); flow_hashtab[b] = sidx; flow_dbg(flow_at_sidx(sidx), "hash table insert: bucket: %u", b); + + return hash; } /** diff --git a/flow.h b/flow.h index 0ba00da..612459e 100644 --- a/flow.h +++ b/flow.h @@ -211,7 +211,7 @@ static inline bool flow_sidx_eq(flow_sidx_t a, flow_sidx_t b) return (a.flow == b.flow) && (a.side == b.side); } -void flow_hash_insert(const struct ctx *c, flow_sidx_t sidx); +uint64_t flow_hash_insert(const struct ctx *c, flow_sidx_t sidx); void flow_hash_remove(const struct ctx *c, flow_sidx_t sidx); flow_sidx_t flow_lookup_af(const struct ctx *c, uint8_t proto, uint8_t pif, sa_family_t af, diff --git a/tcp.c b/tcp.c index 8ab8c4d..91b8a46 100644 --- a/tcp.c +++ b/tcp.c @@ -1575,28 +1575,16 @@ static void tcp_tap_window_update(struct tcp_tap_conn *conn, unsigned wnd) } /** - * tcp_seq_init() - Calculate initial sequence number according to RFC 6528 - * @c: Execution context - * @conn: TCP connection, with faddr, fport and eport populated + * tcp_init_seq() - Calculate initial sequence number according to RFC 6528 + * @hash: Hash of connection details * @now: Current timestamp */ -static void tcp_seq_init(const struct ctx *c, struct tcp_tap_conn *conn, - const struct timespec *now) +static uint32_t tcp_init_seq(uint64_t hash, const struct timespec *now) { - struct siphash_state state = SIPHASH_INIT(c->hash_secret); - const struct flowside *tapside = TAPFLOW(conn); - uint64_t hash; - uint32_t ns; - - inany_siphash_feed(&state, &tapside->faddr); - inany_siphash_feed(&state, &tapside->eaddr); - hash = siphash_final(&state, 36, - (uint64_t)tapside->fport << 16 | tapside->eport); - /* 32ns ticks, overflows 32 bits every 137s */ - ns = (now->tv_sec * 1000000000 + now->tv_nsec) >> 5; + uint32_t ns = (now->tv_sec * 1000000000 + now->tv_nsec) >> 5; - conn->seq_to_tap = ((uint32_t)(hash >> 32) ^ (uint32_t)hash) + ns; + return ((uint32_t)(hash >> 32) ^ (uint32_t)hash) + ns; } /** @@ -1775,6 +1763,7 @@ static void tcp_conn_from_tap(struct ctx *c, sa_family_t af, union sockaddr_inany sa; union flow *flow; int s = -1, mss; + uint64_t hash; socklen_t sl; if (!(flow = flow_alloc())) @@ -1846,11 +1835,10 @@ static void tcp_conn_from_tap(struct ctx *c, sa_family_t af, conn->seq_from_tap = conn->seq_init_from_tap + 1; conn->seq_ack_to_tap = conn->seq_from_tap; - tcp_seq_init(c, conn, now); + hash = flow_hash_insert(c, TAP_SIDX(conn)); + conn->seq_to_tap = tcp_init_seq(hash, now); conn->seq_ack_from_tap = conn->seq_to_tap; - flow_hash_insert(c, TAP_SIDX(conn)); - sockaddr_from_inany(&sa, &sl, &fwd->eaddr, fwd->eport, c->ifi6); if (!bind(s, &sa.sa, sl)) { @@ -2536,6 +2524,7 @@ static void tcp_tap_conn_from_sock(struct ctx *c, in_port_t dstport, union inany_addr saddr, daddr; /* FIXME: avoid bulky temporaries */ struct tcp_tap_conn *conn; in_port_t srcport; + uint64_t hash; inany_from_sockaddr(&saddr, &srcport, sa); tcp_snat_inbound(c, &saddr); @@ -2559,8 +2548,8 @@ static void tcp_tap_conn_from_sock(struct ctx *c, in_port_t dstport, conn->ws_to_tap = conn->ws_from_tap = 0; conn_event(c, conn, SOCK_ACCEPTED); - tcp_seq_init(c, conn, now); - flow_hash_insert(c, TAP_SIDX(conn)); + hash = flow_hash_insert(c, TAP_SIDX(conn)); + conn->seq_to_tap = tcp_init_seq(hash, now); conn->seq_ack_from_tap = conn->seq_to_tap; -- 2.45.0