From cff6d757e3ba609c08ef2aaa00f07e53551e5bf6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 3 Jun 2024 07:11:10 +0200 Subject: Adding upstream version 3.0.0. Signed-off-by: Daniel Baumann --- src/dns_ring.c | 225 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 225 insertions(+) create mode 100644 src/dns_ring.c (limited to 'src/dns_ring.c') diff --git a/src/dns_ring.c b/src/dns_ring.c new file mode 100644 index 0000000..01ce593 --- /dev/null +++ b/src/dns_ring.c @@ -0,0 +1,225 @@ +/* + * Ring buffer management + * This is a fork of ring.c for DNS usage. + * + * Copyright (C) 2000-2019 Willy Tarreau - w@1wt.eu + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation, version 2.1 + * exclusively. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* Initialize a pre-allocated ring with the buffer area + * of size */ +void dns_ring_init(struct dns_ring *ring, void *area, size_t size) +{ + HA_RWLOCK_INIT(&ring->lock); + MT_LIST_INIT(&ring->waiters); + ring->readers_count = 0; + ring->buf = b_make(area, size, 0, 0); + /* write the initial RC byte */ + b_putchr(&ring->buf, 0); +} + +/* Creates and returns a ring buffer of size bytes. Returns NULL on + * allocation failure. + */ +struct dns_ring *dns_ring_new(size_t size) +{ + struct dns_ring *ring = NULL; + void *area = NULL; + + if (size < 2) + goto fail; + + ring = malloc(sizeof(*ring)); + if (!ring) + goto fail; + + area = malloc(size); + if (!area) + goto fail; + + dns_ring_init(ring, area, size); + return ring; + fail: + free(area); + free(ring); + return NULL; +} + +/* destroys and frees ring */ +void dns_ring_free(struct dns_ring *ring) +{ + if (!ring) + return; + + free(ring->buf.area); + free(ring); +} + +/* Tries to send parts from followed by parts from + * to ring . The message is sent atomically. It may be truncated to + * bytes if is non-null. There is no distinction between the + * two lists, it's just a convenience to help the caller prepend some prefixes + * when necessary. It takes the ring's write lock to make sure no other thread + * will touch the buffer during the update. Returns the number of bytes sent, + * or <=0 on failure. + */ +ssize_t dns_ring_write(struct dns_ring *ring, size_t maxlen, const struct ist pfx[], size_t npfx, const struct ist msg[], size_t nmsg) +{ + struct buffer *buf = &ring->buf; + struct appctx *appctx; + size_t totlen = 0; + size_t lenlen; + uint64_t dellen; + int dellenlen; + struct mt_list *elt1, elt2; + ssize_t sent = 0; + int i; + + /* we have to find some room to add our message (the buffer is + * never empty and at least contains the previous counter) and + * to update both the buffer contents and heads at the same + * time (it's doable using atomic ops but not worth the + * trouble, let's just lock). For this we first need to know + * the total message's length. We cannot measure it while + * copying due to the varint encoding of the length. + */ + for (i = 0; i < npfx; i++) + totlen += pfx[i].len; + for (i = 0; i < nmsg; i++) + totlen += msg[i].len; + + if (totlen > maxlen) + totlen = maxlen; + + lenlen = varint_bytes(totlen); + + HA_RWLOCK_WRLOCK(RING_LOCK, &ring->lock); + if (lenlen + totlen + 1 + 1 > b_size(buf)) + goto done_buf; + + while (b_room(buf) < lenlen + totlen + 1) { + /* we need to delete the oldest message (from the end), + * and we have to stop if there's a reader stuck there. + * Unless there's corruption in the buffer it's guaranteed + * that we have enough data to find 1 counter byte, a + * varint-encoded length (1 byte min) and the message + * payload (0 bytes min). + */ + if (*b_head(buf)) + goto done_buf; + dellenlen = b_peek_varint(buf, 1, &dellen); + if (!dellenlen) + goto done_buf; + BUG_ON(b_data(buf) < 1 + dellenlen + dellen); + + b_del(buf, 1 + dellenlen + dellen); + } + + /* OK now we do have room */ + __b_put_varint(buf, totlen); + + totlen = 0; + for (i = 0; i < npfx; i++) { + size_t len = pfx[i].len; + + if (len + totlen > maxlen) + len = maxlen - totlen; + if (len) + __b_putblk(buf, pfx[i].ptr, len); + totlen += len; + } + + for (i = 0; i < nmsg; i++) { + size_t len = msg[i].len; + + if (len + totlen > maxlen) + len = maxlen - totlen; + if (len) + __b_putblk(buf, msg[i].ptr, len); + totlen += len; + } + + *b_tail(buf) = 0; buf->data++; // new read counter + sent = lenlen + totlen + 1; + + /* notify potential readers */ + mt_list_for_each_entry_safe(appctx, &ring->waiters, wait_entry, elt1, elt2) + appctx_wakeup(appctx); + + done_buf: + HA_RWLOCK_WRUNLOCK(RING_LOCK, &ring->lock); + return sent; +} + +/* Tries to attach appctx as a new reader on ring . This is + * meant to be used by low level appctx code such as CLI or ring forwarding. + * For higher level functions, please see the relevant parts in appctx or CLI. + * It returns non-zero on success or zero on failure if too many users are + * already attached. On success, the caller MUST call dns_ring_detach_appctx() + * to detach itself, even if it was never woken up. + */ +int dns_ring_attach(struct dns_ring *ring) +{ + int users = ring->readers_count; + + do { + if (users >= 255) + return 0; + } while (!_HA_ATOMIC_CAS(&ring->readers_count, &users, users + 1)); + return 1; +} + +/* detach an appctx from a ring. The appctx is expected to be waiting at offset + * relative to the beginning of the storage, or ~0 if not waiting yet. + * Nothing is done if is NULL. + */ +void dns_ring_detach_appctx(struct dns_ring *ring, struct appctx *appctx, size_t ofs) +{ + if (!ring) + return; + + HA_RWLOCK_WRLOCK(RING_LOCK, &ring->lock); + if (ofs != ~0) { + /* reader was still attached */ + if (ofs < b_head_ofs(&ring->buf)) + ofs += b_size(&ring->buf) - b_head_ofs(&ring->buf); + else + ofs -= b_head_ofs(&ring->buf); + + BUG_ON(ofs >= b_size(&ring->buf)); + MT_LIST_DELETE(&appctx->wait_entry); + HA_ATOMIC_DEC(b_peek(&ring->buf, ofs)); + } + HA_ATOMIC_DEC(&ring->readers_count); + HA_RWLOCK_WRUNLOCK(RING_LOCK, &ring->lock); +} + +/* + * Local variables: + * c-indent-level: 8 + * c-basic-offset: 8 + * End: + */ -- cgit v1.2.3