From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by passt.top (Postfix) with ESMTPS id D9CEB5A027C for ; Thu, 22 Feb 2024 06:56:09 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202312; t=1708581366; bh=eAgtjeifIAZWYHLGrdQmkonFcftiMbZZkmNvAHQ6lZU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MAbFXGNF0MJUgAAbUYFBPItZ3PlLZ3pAN2UfIAG8CQBcV2DNoPl0zPlaOtY6wM9nj 4qKGJevjskixIxDM3ao4niLGtqmzSqYCDXY6VOxsgwD6mWVDQvd6auVGdbVO/a7jiu BHSiI+UfhYWs2YXVqYbVnicrODcXOSybpvv8SWRp0OxdqNl0EREYM7gxcGtF/k+46x ECiZ2b/8jh2BtlBErZkI2dfmam0Hc6xTYgNtJWrWVqCF6nevg4i8zSkH6E6JlHjepo 8twdZe7l1Pt7lDzdSvmECXcijR4XlNNQB9+yQ7ib0p86LbbQ3h1utdmeW0EJHfZ2RR Ws1SYDrCaUVeg== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4TgMny2ZSXz4wcR; Thu, 22 Feb 2024 16:56:06 +1100 (AEDT) From: David Gibson To: passt-dev@passt.top, Stefano Brivio , Laurent Vivier Subject: [PATCH 1/6] util: Add helper to find offset into io vector Date: Thu, 22 Feb 2024 16:55:57 +1100 Message-ID: <20240222055602.1872516-2-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240222055602.1872516-1-david@gibson.dropbear.id.au> References: <20240222055602.1872516-1-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: CTN627NRON7BMDLGIINKW5ZQNFOPH233 X-Message-ID-Hash: CTN627NRON7BMDLGIINKW5ZQNFOPH233 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: tap_send_frames_passt() needs to determine which buffer element a byte offset into an IO vector lies in. We have some upcoming uses for similar logic, so split this out into a helper function iov_offset(). Signed-off-by: David Gibson --- tap.c | 13 +++++-------- util.c | 23 +++++++++++++++++++++++ util.h | 1 + 3 files changed, 29 insertions(+), 8 deletions(-) diff --git a/tap.c b/tap.c index 396dee7e..f15eba6e 100644 --- a/tap.c +++ b/tap.c @@ -390,22 +390,19 @@ static size_t tap_send_frames_passt(const struct ctx *c, .msg_iovlen = n, }; unsigned int i; + size_t offset; ssize_t sent; sent = sendmsg(c->fd_tap, &mh, MSG_NOSIGNAL | MSG_DONTWAIT); if (sent < 0) return 0; - /* Check for any partial frames due to short send */ - for (i = 0; i < n; i++) { - if ((size_t)sent < iov[i].iov_len) - break; - sent -= iov[i].iov_len; - } + offset = (size_t)sent; + i = iov_offset(iov, n, &offset); - if (i < n && sent) { + if (i < n && offset) { /* A partial frame was sent */ - tap_send_remainder(c, &iov[i], sent); + tap_send_remainder(c, &iov[i], offset); i++; } diff --git a/util.c b/util.c index 21b35ff9..fb6a0430 100644 --- a/util.c +++ b/util.c @@ -574,3 +574,26 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags, return clone(fn, stack_area + stack_size / 2, flags, arg); #endif } + +/* iov_offset() - interpret offset into an IO vector + * @iov: IO vector + * @n: Number of entries in @iov + * @offset: Pointer to offset into IO vector + * + * Return: index I of iovec which contains the given offset, or @n if + * the given offset is >= the total # of bytes in the vector. + * *@offset is updated to be the byte offset into (@iov + I), + * and is guaranteed to be less than @iov[I].iov_len + */ +size_t iov_offset(const struct iovec *iov, size_t n, size_t *offset) +{ + size_t i; + + for (i = 0; i < n; i++) { + if (*offset < iov[i].iov_len) + break; + *offset -= iov[i].iov_len; + } + + return i; +} diff --git a/util.h b/util.h index d2320f8c..62fad6fe 100644 --- a/util.h +++ b/util.h @@ -229,6 +229,7 @@ void write_pidfile(int fd, pid_t pid); int __daemon(int pidfile_fd, int devnull_fd); int fls(unsigned long x); int write_file(const char *path, const char *buf); +size_t iov_offset(const struct iovec *iov, size_t n, size_t *offset); /** * mod_sub() - Modular arithmetic subtraction -- 2.43.2