From fb5d1c5d7d0b914a90aaeecf406c7092d9d55aeb Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 19 Oct 2022 11:43:51 +1100 Subject: tap: Remove unhelpeful vnet_pre optimization from tap_send() Callers of tap_send() can optionally use a small optimization by adding extra space for the 4 byte length header used on the qemu socket interface. tap_ip_send() is currently the only user of this, but this is used only for "slow path" ICMP and DHCP packets, so there's not a lot of value to the optimization. Worse, having the two paths here complicates the interface and makes future cleanups difficult, so just remove it. I have some plans to bring back the optimization in a more general way in future, but for now it's just in the way. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- arp.c | 2 +- dhcp.c | 2 +- ndp.c | 2 +- tap.c | 29 +++++++++-------------------- tap.h | 2 +- 5 files changed, 13 insertions(+), 24 deletions(-) diff --git a/arp.c b/arp.c index 0ad97af..141d43f 100644 --- a/arp.c +++ b/arp.c @@ -81,7 +81,7 @@ int arp(const struct ctx *c, const struct pool *p) memcpy(eh->h_dest, eh->h_source, sizeof(eh->h_dest)); memcpy(eh->h_source, c->mac, sizeof(eh->h_source)); - if (tap_send(c, eh, len, 0) < 0) + if (tap_send(c, eh, len) < 0) perror("ARP: send"); return 1; diff --git a/dhcp.c b/dhcp.c index 875e18b..2b3af82 100644 --- a/dhcp.c +++ b/dhcp.c @@ -377,7 +377,7 @@ int dhcp(const struct ctx *c, const struct pool *p) memcpy(eh->h_dest, eh->h_source, ETH_ALEN); memcpy(eh->h_source, c->mac, ETH_ALEN); - if (tap_send(c, eh, len, 0) < 0) + if (tap_send(c, eh, len) < 0) perror("DHCP: send"); return 1; diff --git a/ndp.c b/ndp.c index 03f1d06..79be0cf 100644 --- a/ndp.c +++ b/ndp.c @@ -200,7 +200,7 @@ dns_done: memcpy(ehr->h_source, c->mac, ETH_ALEN); ehr->h_proto = htons(ETH_P_IPV6); - if (tap_send(c, ehr, len, 0) < 0) + if (tap_send(c, ehr, len) < 0) perror("NDP: send"); return 1; diff --git a/tap.c b/tap.c index 844ee43..07592dd 100644 --- a/tap.c +++ b/tap.c @@ -66,34 +66,24 @@ static PACKET_POOL_NOINIT(pool_tap6, TAP_MSGS, pkt_buf); * @c: Execution context * @data: Packet buffer * @len: Total L2 packet length - * @vnet_pre: Buffer has four-byte headroom * * Return: return code from send() or write() */ -int tap_send(const struct ctx *c, const void *data, size_t len, int vnet_pre) +int tap_send(const struct ctx *c, const void *data, size_t len) { - if (vnet_pre) - pcap((char *)data + 4, len); - else - pcap(data, len); + pcap(data, len); if (c->mode == MODE_PASST) { int flags = MSG_NOSIGNAL | MSG_DONTWAIT; + uint32_t vnet_len = htonl(len); - if (vnet_pre) { - *((uint32_t *)data) = htonl(len); - len += 4; - } else { - uint32_t vnet_len = htonl(len); - - if (send(c->fd_tap, &vnet_len, 4, flags) < 0) - return -1; - } + if (send(c->fd_tap, &vnet_len, 4, flags) < 0) + return -1; return send(c->fd_tap, data, len, flags); } - return write(c->fd_tap, (char *)data + (vnet_pre ? 4 : 0), len); + return write(c->fd_tap, (char *)data, len); } /** @@ -135,10 +125,9 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, const char *in, size_t len, uint32_t flow) { char buf[USHRT_MAX]; - char *pkt = buf + 4; struct ethhdr *eh; - eh = (struct ethhdr *)pkt; + eh = (struct ethhdr *)buf; /* TODO: ARP table lookup */ memcpy(eh->h_dest, c->mac_guest, ETH_ALEN); @@ -174,7 +163,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, csum_icmp4(ih, ih + 1, len - sizeof(*ih)); } - if (tap_send(c, buf, len + sizeof(*iph) + sizeof(*eh), 1) < 0) + if (tap_send(c, buf, len + sizeof(*iph) + sizeof(*eh)) < 0) debug("tap: failed to send %lu bytes (IPv4)", len); } else { struct ipv6hdr *ip6h = (struct ipv6hdr *)(eh + 1); @@ -215,7 +204,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, ip6h->flow_lbl[2] = (flow >> 0) & 0xff; } - if (tap_send(c, buf, len + sizeof(*ip6h) + sizeof(*eh), 1) < 1) + if (tap_send(c, buf, len + sizeof(*ip6h) + sizeof(*eh)) < 1) debug("tap: failed to send %lu bytes (IPv6)", len); } } diff --git a/tap.h b/tap.h index a6764b4..a8da8bb 100644 --- a/tap.h +++ b/tap.h @@ -11,7 +11,7 @@ const struct in6_addr *tap_ip6_daddr(const struct ctx *c, const struct in6_addr *src); void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, const char *in, size_t len, uint32_t flow); -int tap_send(const struct ctx *c, const void *data, size_t len, int vnet_pre); +int tap_send(const struct ctx *c, const void *data, size_t len); void tap_handler(struct ctx *c, int fd, uint32_t events, const struct timespec *now); void tap_sock_init(struct ctx *c); -- cgit v1.2.3