From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by passt.top (Postfix) with ESMTPS id 6C4EA5A0270 for ; Fri, 9 Dec 2022 06:42:37 +0100 (CET) Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4NT0KM2m17z4xbN; Fri, 9 Dec 2022 16:42:31 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=201602; t=1670564551; bh=84suzu7IOGPMRHk7XVAYrA5t96BlA5JX+EAZk9UZUQw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FIY6adaqduScrjkd01img9OBvgx+uMmKVYwzlrEuxzqMF81eLYSciZGyYax23ccA3 PyGQrR0cO2pp9ua7zCKxuqKg5Tx535nPdiRUICjbjeQIti6lgI6ydbKCLOEhL1bRG6 b2EUteRUGKVixKPiW8zacbEM6AQVems/zs3xppcU= From: David Gibson To: Stefano Brivio , passt-dev@passt.top Subject: [PATCH v2 04/18] tcp: Don't keep compute total bytes in a message until we need it Date: Fri, 9 Dec 2022 16:42:14 +1100 Message-Id: <20221209054228.4085990-5-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221209054228.4085990-1-david@gibson.dropbear.id.au> References: <20221209054228.4085990-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: 2MKGA5QAKEM5LH5O27MLTTRMD6CGDBJO X-Message-ID-Hash: 2MKGA5QAKEM5LH5O27MLTTRMD6CGDBJO 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: 3.3.3 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: tcp[46]_l2_buf_bytes keep track of the total number of bytes we have queued to send to the tap interface. tcp_l2_buf_flush_passt() uses this to determine if sendmsg() has sent all the data we requested, or whether we need to resend a trailing portion. However, the logic for finding where we're up to in the case of a short sendmsg() can equally well tell whether we've had one at all, without knowing the total number in advance. This does require an extra loop after each sendmsg(), but it's doing simple arithmetic on values we've already been accessing, and it leads to overall simpler code. tcp[46]_l2_flags_buf_bytes were being calculated, but never used for anything, so simply remove them. Signed-off-by: David Gibson --- tcp.c | 55 +++++++++++++++++++------------------------------------ 1 file changed, 19 insertions(+), 36 deletions(-) diff --git a/tcp.c b/tcp.c index fe788b4..4050ea6 100644 --- a/tcp.c +++ b/tcp.c @@ -476,7 +476,6 @@ static struct tcp4_l2_buf_t { tcp4_l2_buf[TCP_FRAMES_MEM]; static unsigned int tcp4_l2_buf_used; -static size_t tcp4_l2_buf_bytes; /** * tcp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections @@ -507,7 +506,6 @@ struct tcp6_l2_buf_t { tcp6_l2_buf[TCP_FRAMES_MEM]; static unsigned int tcp6_l2_buf_used; -static size_t tcp6_l2_buf_bytes; /* recvmsg()/sendmsg() data for tap */ static char tcp_buf_discard [MAX_WINDOW]; @@ -555,7 +553,6 @@ static struct tcp4_l2_flags_buf_t { tcp4_l2_flags_buf[TCP_FRAMES_MEM]; static unsigned int tcp4_l2_flags_buf_used; -static size_t tcp4_l2_flags_buf_bytes; /** * tcp6_l2_flags_buf_t - IPv6 packet buffers for segments without data (flags) @@ -585,7 +582,6 @@ static struct tcp6_l2_flags_buf_t { tcp6_l2_flags_buf[TCP_FRAMES_MEM]; static unsigned int tcp6_l2_flags_buf_used; -static size_t tcp6_l2_flags_buf_bytes; /* TCP connections */ union tcp_conn tc[TCP_MAX_CONNS]; @@ -1418,19 +1414,17 @@ static int tcp_l2_buf_write_one(struct ctx *c, const struct iovec *iov) * tcp_l2_buf_flush_passt() - Send a message on the passt tap interface * @c: Execution context * @mh: Message header that was partially sent by sendmsg() - * @buf_bytes: Total number of bytes to send */ -static void tcp_l2_buf_flush_passt(const struct ctx *c, - const struct msghdr *mh, size_t buf_bytes) +static void tcp_l2_buf_flush_passt(const struct ctx *c, const struct msghdr *mh) { - size_t end = 0, missing, sent; + size_t end = 0, missing; struct iovec *iov; unsigned int i; - ssize_t n; + ssize_t sent; char *p; - n = sendmsg(c->fd_tap, mh, MSG_NOSIGNAL | MSG_DONTWAIT); - if (n < 0 || ((sent = (size_t)n) == buf_bytes)) + sent = sendmsg(c->fd_tap, mh, MSG_NOSIGNAL | MSG_DONTWAIT); + if (sent < 0) return; /* Ensure a complete last message on partial sendmsg() */ @@ -1441,6 +1435,9 @@ static void tcp_l2_buf_flush_passt(const struct ctx *c, } missing = end - sent; + if (!missing) + return; + p = (char *)iov->iov_base + iov->iov_len - missing; if (send(c->fd_tap, p, missing, MSG_NOSIGNAL)) debug("TCP: failed to flush %lu missing bytes to tap", missing); @@ -1451,19 +1448,18 @@ static void tcp_l2_buf_flush_passt(const struct ctx *c, * @c: Execution context * @mh: Message header pointing to buffers, msg_iovlen not set * @buf_used: Pointer to count of used buffers, set to 0 on return - * @buf_bytes: Pointer to count of buffer bytes, set to 0 on return */ static void tcp_l2_buf_flush(struct ctx *c, struct msghdr *mh, - unsigned int *buf_used, size_t *buf_bytes) + unsigned int *buf_used) { + size_t i; + if (!(mh->msg_iovlen = *buf_used)) return; if (c->mode == MODE_PASST) { - tcp_l2_buf_flush_passt(c, mh, *buf_bytes); + tcp_l2_buf_flush_passt(c, mh); } else { - size_t i; - for (i = 0; i < mh->msg_iovlen; i++) { struct iovec *iov = &mh->msg_iov[i]; @@ -1471,7 +1467,7 @@ static void tcp_l2_buf_flush(struct ctx *c, struct msghdr *mh, i--; } } - *buf_used = *buf_bytes = 0; + *buf_used = 0; pcap_multiple(mh->msg_iov, mh->msg_iovlen, sizeof(uint32_t)); } @@ -1484,17 +1480,14 @@ static void tcp_l2_flags_buf_flush(struct ctx *c) { struct msghdr mh = { 0 }; unsigned int *buf_used; - size_t *buf_bytes; mh.msg_iov = tcp6_l2_flags_iov; buf_used = &tcp6_l2_flags_buf_used; - buf_bytes = &tcp6_l2_flags_buf_bytes; - tcp_l2_buf_flush(c, &mh, buf_used, buf_bytes); + tcp_l2_buf_flush(c, &mh, buf_used); mh.msg_iov = tcp4_l2_flags_iov; buf_used = &tcp4_l2_flags_buf_used; - buf_bytes = &tcp4_l2_flags_buf_bytes; - tcp_l2_buf_flush(c, &mh, buf_used, buf_bytes); + tcp_l2_buf_flush(c, &mh, buf_used); } /** @@ -1505,17 +1498,14 @@ static void tcp_l2_data_buf_flush(struct ctx *c) { struct msghdr mh = { 0 }; unsigned int *buf_used; - size_t *buf_bytes; mh.msg_iov = tcp6_l2_iov; buf_used = &tcp6_l2_buf_used; - buf_bytes = &tcp6_l2_buf_bytes; - tcp_l2_buf_flush(c, &mh, buf_used, buf_bytes); + tcp_l2_buf_flush(c, &mh, buf_used); mh.msg_iov = tcp4_l2_iov; buf_used = &tcp4_l2_buf_used; - buf_bytes = &tcp4_l2_buf_bytes; - tcp_l2_buf_flush(c, &mh, buf_used, buf_bytes); + tcp_l2_buf_flush(c, &mh, buf_used); } /** @@ -1829,11 +1819,6 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) NULL, conn->seq_to_tap); iov->iov_len = eth_len + sizeof(uint32_t); - if (CONN_V4(conn)) - tcp4_l2_flags_buf_bytes += iov->iov_len; - else - tcp6_l2_flags_buf_bytes += iov->iov_len; - if (th->ack) conn_flag(c, conn, ~ACK_TO_TAP_DUE); @@ -1849,7 +1834,6 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) memcpy(b4 + 1, b4, sizeof(*b4)); (iov + 1)->iov_len = iov->iov_len; tcp4_l2_flags_buf_used++; - tcp4_l2_flags_buf_bytes += iov->iov_len; } if (tcp4_l2_flags_buf_used > ARRAY_SIZE(tcp4_l2_flags_buf) - 2) @@ -1859,7 +1843,6 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) memcpy(b6 + 1, b6, sizeof(*b6)); (iov + 1)->iov_len = iov->iov_len; tcp6_l2_flags_buf_used++; - tcp6_l2_flags_buf_bytes += iov->iov_len; } if (tcp6_l2_flags_buf_used > ARRAY_SIZE(tcp6_l2_flags_buf) - 2) @@ -2203,7 +2186,7 @@ static void tcp_data_to_tap(struct ctx *c, struct tcp_tap_conn *conn, len = tcp_l2_buf_fill_headers(c, conn, b, plen, check, seq); iov = tcp4_l2_iov + tcp4_l2_buf_used++; - tcp4_l2_buf_bytes += iov->iov_len = len + sizeof(b->vnet_len); + iov->iov_len = len + sizeof(b->vnet_len); if (tcp4_l2_buf_used > ARRAY_SIZE(tcp4_l2_buf) - 1) tcp_l2_data_buf_flush(c); } else if (CONN_V6(conn)) { @@ -2212,7 +2195,7 @@ static void tcp_data_to_tap(struct ctx *c, struct tcp_tap_conn *conn, len = tcp_l2_buf_fill_headers(c, conn, b, plen, NULL, seq); iov = tcp6_l2_iov + tcp6_l2_buf_used++; - tcp6_l2_buf_bytes += iov->iov_len = len + sizeof(b->vnet_len); + iov->iov_len = len + sizeof(b->vnet_len); if (tcp6_l2_buf_used > ARRAY_SIZE(tcp6_l2_buf) - 1) tcp_l2_data_buf_flush(c); } -- 2.38.1