diff options
Diffstat (limited to 'tcp_buf.c')
| -rw-r--r-- | tcp_buf.c | 519 |
1 files changed, 519 insertions, 0 deletions
diff --git a/tcp_buf.c b/tcp_buf.c new file mode 100644 index 0000000..5f4df5b --- /dev/null +++ b/tcp_buf.c @@ -0,0 +1,519 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +/* PASST - Plug A Simple Socket Transport + * for qemu/UNIX domain socket mode + * + * PASTA - Pack A Subtle Tap Abstraction + * for network namespace/tap device mode + * + * tcp_buf.c - TCP L2 buffer management functions + * + * Copyright Red Hat + * Author: Stefano Brivio <sbrivio@redhat.com> + */ + +#include <stddef.h> +#include <stdint.h> +#include <limits.h> +#include <string.h> +#include <errno.h> + +#include <netinet/ip.h> + +#include <linux/tcp.h> + +#include "util.h" +#include "ip.h" +#include "iov.h" +#include "passt.h" +#include "tap.h" +#include "siphash.h" +#include "inany.h" +#include "tcp_conn.h" +#include "tcp_internal.h" +#include "tcp_buf.h" + +#define TCP_FRAMES_MEM 128 +#define TCP_FRAMES \ + (c->mode == MODE_PASST ? TCP_FRAMES_MEM : 1) + +/* Static buffers */ +/** + * struct tcp_payload_t - TCP header and data to send segments with payload + * @th: TCP header + * @data: TCP data + */ +struct tcp_payload_t { + struct tcphdr th; + uint8_t data[IP_MAX_MTU - sizeof(struct tcphdr)]; +#ifdef __AVX2__ +} __attribute__ ((packed, aligned(32))); /* For AVX2 checksum routines */ +#else +} __attribute__ ((packed, aligned(__alignof__(unsigned int)))); +#endif + +/** + * struct tcp_flags_t - TCP header and data to send zero-length + * segments (flags) + * @th: TCP header + * @opts TCP options + */ +struct tcp_flags_t { + struct tcphdr th; + char opts[OPT_MSS_LEN + OPT_WS_LEN + 1]; +#ifdef __AVX2__ +} __attribute__ ((packed, aligned(32))); +#else +} __attribute__ ((packed, aligned(__alignof__(unsigned int)))); +#endif + +/* Ethernet header for IPv4 frames */ +static struct ethhdr tcp4_eth_src; + +static struct tap_hdr tcp4_payload_tap_hdr[TCP_FRAMES_MEM]; +/* IPv4 headers */ +static struct iphdr tcp4_payload_ip[TCP_FRAMES_MEM]; +/* TCP segments with payload for IPv4 frames */ +static struct tcp_payload_t tcp4_payload[TCP_FRAMES_MEM]; + +static_assert(MSS4 <= sizeof(tcp4_payload[0].data), "MSS4 is greater than 65516"); + +/* References tracking the owner connection of frames in the tap outqueue */ +static struct tcp_tap_conn *tcp4_frame_conns[TCP_FRAMES_MEM]; +static unsigned int tcp4_payload_used; + +static struct tap_hdr tcp4_flags_tap_hdr[TCP_FRAMES_MEM]; +/* IPv4 headers for TCP segment without payload */ +static struct iphdr tcp4_flags_ip[TCP_FRAMES_MEM]; +/* TCP segments without payload for IPv4 frames */ +static struct tcp_flags_t tcp4_flags[TCP_FRAMES_MEM]; + +static unsigned int tcp4_flags_used; + +/* Ethernet header for IPv6 frames */ +static struct ethhdr tcp6_eth_src; + +static struct tap_hdr tcp6_payload_tap_hdr[TCP_FRAMES_MEM]; +/* IPv6 headers */ +static struct ipv6hdr tcp6_payload_ip[TCP_FRAMES_MEM]; +/* TCP headers and data for IPv6 frames */ +static struct tcp_payload_t tcp6_payload[TCP_FRAMES_MEM]; + +static_assert(MSS6 <= sizeof(tcp6_payload[0].data), "MSS6 is greater than 65516"); + +/* References tracking the owner connection of frames in the tap outqueue */ +static struct tcp_tap_conn *tcp6_frame_conns[TCP_FRAMES_MEM]; +static unsigned int tcp6_payload_used; + +static struct tap_hdr tcp6_flags_tap_hdr[TCP_FRAMES_MEM]; +/* IPv6 headers for TCP segment without payload */ +static struct ipv6hdr tcp6_flags_ip[TCP_FRAMES_MEM]; +/* TCP segment without payload for IPv6 frames */ +static struct tcp_flags_t tcp6_flags[TCP_FRAMES_MEM]; + +static unsigned int tcp6_flags_used; + +/* recvmsg()/sendmsg() data for tap */ +static struct iovec iov_sock [TCP_FRAMES_MEM + 1]; + +static struct iovec tcp4_l2_iov [TCP_FRAMES_MEM][TCP_NUM_IOVS]; +static struct iovec tcp6_l2_iov [TCP_FRAMES_MEM][TCP_NUM_IOVS]; +static struct iovec tcp4_l2_flags_iov [TCP_FRAMES_MEM][TCP_NUM_IOVS]; +static struct iovec tcp6_l2_flags_iov [TCP_FRAMES_MEM][TCP_NUM_IOVS]; +/** + * tcp_update_l2_buf() - Update Ethernet header buffers with addresses + * @eth_d: Ethernet destination address, NULL if unchanged + * @eth_s: Ethernet source address, NULL if unchanged + */ +void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s) +{ + eth_update_mac(&tcp4_eth_src, eth_d, eth_s); + eth_update_mac(&tcp6_eth_src, eth_d, eth_s); +} + +/** + * tcp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets + * @c: Execution context + */ +void tcp_sock4_iov_init(const struct ctx *c) +{ + struct iphdr iph = L2_BUF_IP4_INIT(IPPROTO_TCP); + struct iovec *iov; + int i; + + tcp4_eth_src.h_proto = htons_constant(ETH_P_IP); + + for (i = 0; i < ARRAY_SIZE(tcp4_payload); i++) { + tcp4_payload_ip[i] = iph; + tcp4_payload[i].th.doff = sizeof(struct tcphdr) / 4; + tcp4_payload[i].th.ack = 1; + } + + for (i = 0; i < ARRAY_SIZE(tcp4_flags); i++) { + tcp4_flags_ip[i] = iph; + tcp4_flags[i].th.doff = sizeof(struct tcphdr) / 4; + tcp4_flags[i].th.ack = 1; + } + + for (i = 0; i < TCP_FRAMES_MEM; i++) { + iov = tcp4_l2_iov[i]; + + iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_payload_tap_hdr[i]); + iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp4_eth_src); + iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_payload_ip[i]); + iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_payload[i]; + } + + for (i = 0; i < TCP_FRAMES_MEM; i++) { + iov = tcp4_l2_flags_iov[i]; + + iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp4_flags_tap_hdr[i]); + iov[TCP_IOV_ETH].iov_base = &tcp4_eth_src; + iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp4_eth_src); + iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_flags_ip[i]); + iov[TCP_IOV_PAYLOAD].iov_base = &tcp4_flags[i]; + } +} + +/** + * tcp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets + * @c: Execution context + */ +void tcp_sock6_iov_init(const struct ctx *c) +{ + struct ipv6hdr ip6 = L2_BUF_IP6_INIT(IPPROTO_TCP); + struct iovec *iov; + int i; + + tcp6_eth_src.h_proto = htons_constant(ETH_P_IPV6); + + for (i = 0; i < ARRAY_SIZE(tcp6_payload); i++) { + tcp6_payload_ip[i] = ip6; + tcp6_payload[i].th.doff = sizeof(struct tcphdr) / 4; + tcp6_payload[i].th.ack = 1; + } + + for (i = 0; i < ARRAY_SIZE(tcp6_flags); i++) { + tcp6_flags_ip[i] = ip6; + tcp6_flags[i].th.doff = sizeof(struct tcphdr) / 4; + tcp6_flags[i].th .ack = 1; + } + + for (i = 0; i < TCP_FRAMES_MEM; i++) { + iov = tcp6_l2_iov[i]; + + iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_payload_tap_hdr[i]); + iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp6_eth_src); + iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_payload_ip[i]); + iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_payload[i]; + } + + for (i = 0; i < TCP_FRAMES_MEM; i++) { + iov = tcp6_l2_flags_iov[i]; + + iov[TCP_IOV_TAP] = tap_hdr_iov(c, &tcp6_flags_tap_hdr[i]); + iov[TCP_IOV_ETH] = IOV_OF_LVALUE(tcp6_eth_src); + iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp6_flags_ip[i]); + iov[TCP_IOV_PAYLOAD].iov_base = &tcp6_flags[i]; + } +} + +/** + * tcp_flags_flush() - Send out buffers for segments with no data (flags) + * @c: Execution context + */ +void tcp_flags_flush(const struct ctx *c) +{ + tap_send_frames(c, &tcp6_l2_flags_iov[0][0], TCP_NUM_IOVS, + tcp6_flags_used); + tcp6_flags_used = 0; + + tap_send_frames(c, &tcp4_l2_flags_iov[0][0], TCP_NUM_IOVS, + tcp4_flags_used); + tcp4_flags_used = 0; +} + +/** + * tcp_revert_seq() - Revert affected conn->seq_to_tap after failed transmission + * @conns: Array of connection pointers corresponding to queued frames + * @frames: Two-dimensional array containing queued frames with sub-iovs + * @num_frames: Number of entries in the two arrays to be compared + */ +static void tcp_revert_seq(struct tcp_tap_conn **conns, struct iovec (*frames)[TCP_NUM_IOVS], + int num_frames) +{ + int i; + + for (i = 0; i < num_frames; i++) { + const struct tcphdr *th = frames[i][TCP_IOV_PAYLOAD].iov_base; + struct tcp_tap_conn *conn = conns[i]; + uint32_t seq = ntohl(th->seq); + + if (SEQ_LE(conn->seq_to_tap, seq)) + continue; + + conn->seq_to_tap = seq; + } +} + +/** + * tcp_payload_flush() - Send out buffers for segments with data + * @c: Execution context + */ +void tcp_payload_flush(const struct ctx *c) +{ + size_t m; + + m = tap_send_frames(c, &tcp6_l2_iov[0][0], TCP_NUM_IOVS, + tcp6_payload_used); + if (m != tcp6_payload_used) { + tcp_revert_seq(&tcp6_frame_conns[m], &tcp6_l2_iov[m], + tcp6_payload_used - m); + } + tcp6_payload_used = 0; + + m = tap_send_frames(c, &tcp4_l2_iov[0][0], TCP_NUM_IOVS, + tcp4_payload_used); + if (m != tcp4_payload_used) { + tcp_revert_seq(&tcp4_frame_conns[m], &tcp4_l2_iov[m], + tcp4_payload_used - m); + } + tcp4_payload_used = 0; +} + +/** + * tcp_buf_send_flag() - Send segment with flags to tap (no payload) + * @c: Execution context + * @conn: Connection pointer + * @flags: TCP flags: if not set, send segment only if ACK is due + * + * Return: negative error code on connection reset, 0 otherwise + */ +int tcp_buf_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags) +{ + struct tcp_flags_t *payload; + struct iovec *iov; + size_t optlen; + size_t l4len; + uint32_t seq; + int ret; + + if (CONN_V4(conn)) + iov = tcp4_l2_flags_iov[tcp4_flags_used++]; + else + iov = tcp6_l2_flags_iov[tcp6_flags_used++]; + + payload = iov[TCP_IOV_PAYLOAD].iov_base; + + seq = conn->seq_to_tap; + ret = tcp_prepare_flags(c, conn, flags, &payload->th, + payload->opts, &optlen); + if (ret <= 0) { + if (CONN_V4(conn)) + tcp4_flags_used--; + else + tcp6_flags_used--; + return ret; + } + + l4len = tcp_l2_buf_fill_headers(c, conn, iov, optlen, NULL, seq); + iov[TCP_IOV_PAYLOAD].iov_len = l4len; + + if (flags & DUP_ACK) { + struct iovec *dup_iov; + int i; + + if (CONN_V4(conn)) + dup_iov = tcp4_l2_flags_iov[tcp4_flags_used++]; + else + dup_iov = tcp6_l2_flags_iov[tcp6_flags_used++]; + + for (i = 0; i < TCP_NUM_IOVS; i++) + memcpy(dup_iov[i].iov_base, iov[i].iov_base, + iov[i].iov_len); + dup_iov[TCP_IOV_PAYLOAD].iov_len = iov[TCP_IOV_PAYLOAD].iov_len; + } + + if (CONN_V4(conn)) { + if (tcp4_flags_used > TCP_FRAMES_MEM - 2) + tcp_flags_flush(c); + } else { + if (tcp6_flags_used > TCP_FRAMES_MEM - 2) + tcp_flags_flush(c); + } + + return 0; +} + +/** + * tcp_data_to_tap() - Finalise (queue) highest-numbered scatter-gather buffer + * @c: Execution context + * @conn: Connection pointer + * @dlen: TCP payload length + * @no_csum: Don't compute IPv4 checksum, use the one from previous buffer + * @seq: Sequence number to be sent + */ +static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn, + ssize_t dlen, int no_csum, uint32_t seq) +{ + struct iovec *iov; + size_t l4len; + + conn->seq_to_tap = seq + dlen; + + if (CONN_V4(conn)) { + struct iovec *iov_prev = tcp4_l2_iov[tcp4_payload_used - 1]; + const uint16_t *check = NULL; + + if (no_csum) { + struct iphdr *iph = iov_prev[TCP_IOV_IP].iov_base; + check = &iph->check; + } + + tcp4_frame_conns[tcp4_payload_used] = conn; + + iov = tcp4_l2_iov[tcp4_payload_used++]; + l4len = tcp_l2_buf_fill_headers(c, conn, iov, dlen, check, seq); + iov[TCP_IOV_PAYLOAD].iov_len = l4len; + if (tcp4_payload_used > TCP_FRAMES_MEM - 1) + tcp_payload_flush(c); + } else if (CONN_V6(conn)) { + tcp6_frame_conns[tcp6_payload_used] = conn; + + iov = tcp6_l2_iov[tcp6_payload_used++]; + l4len = tcp_l2_buf_fill_headers(c, conn, iov, dlen, NULL, seq); + iov[TCP_IOV_PAYLOAD].iov_len = l4len; + if (tcp6_payload_used > TCP_FRAMES_MEM - 1) + tcp_payload_flush(c); + } +} + +/** + * tcp_buf_data_from_sock() - Handle new data from socket, queue to tap, in window + * @c: Execution context + * @conn: Connection pointer + * + * Return: negative on connection reset, 0 otherwise + * + * #syscalls recvmsg + */ +int tcp_buf_data_from_sock(struct ctx *c, struct tcp_tap_conn *conn) +{ + uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap; + int fill_bufs, send_bufs = 0, last_len, iov_rem = 0; + int sendlen, len, dlen, v4 = CONN_V4(conn); + int s = conn->sock, i, ret = 0; + struct msghdr mh_sock = { 0 }; + uint16_t mss = MSS_GET(conn); + uint32_t already_sent, seq; + struct iovec *iov; + + already_sent = conn->seq_to_tap - conn->seq_ack_from_tap; + + if (SEQ_LT(already_sent, 0)) { + /* RFC 761, section 2.1. */ + flow_trace(conn, "ACK sequence gap: ACK for %u, sent: %u", + conn->seq_ack_from_tap, conn->seq_to_tap); + conn->seq_to_tap = conn->seq_ack_from_tap; + already_sent = 0; + } + + if (!wnd_scaled || already_sent >= wnd_scaled) { + conn_flag(c, conn, STALLED); + conn_flag(c, conn, ACK_FROM_TAP_DUE); + return 0; + } + + /* Set up buffer descriptors we'll fill completely and partially. */ + fill_bufs = DIV_ROUND_UP(wnd_scaled - already_sent, mss); + if (fill_bufs > TCP_FRAMES) { + fill_bufs = TCP_FRAMES; + iov_rem = 0; + } else { + iov_rem = (wnd_scaled - already_sent) % mss; + } + + mh_sock.msg_iov = iov_sock; + mh_sock.msg_iovlen = fill_bufs + 1; + + iov_sock[0].iov_base = tcp_buf_discard; + iov_sock[0].iov_len = already_sent; + + if (( v4 && tcp4_payload_used + fill_bufs > TCP_FRAMES_MEM) || + (!v4 && tcp6_payload_used + fill_bufs > TCP_FRAMES_MEM)) { + tcp_payload_flush(c); + + /* Silence Coverity CWE-125 false positive */ + tcp4_payload_used = tcp6_payload_used = 0; + } + + for (i = 0, iov = iov_sock + 1; i < fill_bufs; i++, iov++) { + if (v4) + iov->iov_base = &tcp4_payload[tcp4_payload_used + i].data; + else + iov->iov_base = &tcp6_payload[tcp6_payload_used + i].data; + iov->iov_len = mss; + } + if (iov_rem) + iov_sock[fill_bufs].iov_len = iov_rem; + + /* Receive into buffers, don't dequeue until acknowledged by guest. */ + do + len = recvmsg(s, &mh_sock, MSG_PEEK); + while (len < 0 && errno == EINTR); + + if (len < 0) + goto err; + + if (!len) { + if ((conn->events & (SOCK_FIN_RCVD | TAP_FIN_SENT)) == SOCK_FIN_RCVD) { + if ((ret = tcp_buf_send_flag(c, conn, FIN | ACK))) { + tcp_rst(c, conn); + return ret; + } + + conn_event(c, conn, TAP_FIN_SENT); + } + + return 0; + } + + sendlen = len - already_sent; + if (sendlen <= 0) { + conn_flag(c, conn, STALLED); + return 0; + } + + conn_flag(c, conn, ~STALLED); + + send_bufs = DIV_ROUND_UP(sendlen, mss); + last_len = sendlen - (send_bufs - 1) * mss; + + /* Likely, some new data was acked too. */ + tcp_update_seqack_wnd(c, conn, 0, NULL); + + /* Finally, queue to tap */ + dlen = mss; + seq = conn->seq_to_tap; + for (i = 0; i < send_bufs; i++) { + int no_csum = i && i != send_bufs - 1 && tcp4_payload_used; + + if (i == send_bufs - 1) + dlen = last_len; + + tcp_data_to_tap(c, conn, dlen, no_csum, seq); + seq += dlen; + } + + conn_flag(c, conn, ACK_FROM_TAP_DUE); + + return 0; + +err: + if (errno != EAGAIN && errno != EWOULDBLOCK) { + ret = -errno; + tcp_rst(c, conn); + } + + return ret; +} |