From 4b2d227c8671a4bc37a7288f11d797fd8ba255ca Mon Sep 17 00:00:00 2001 From: David Gibson Date: Thu, 24 Nov 2022 19:54:20 +1100 Subject: [PATCH] udp: Preadjust udp[46]_l2_iov_tap[].iov_base for pasta mode Currently, we always populate udp[46]_l2_iov_tap[].iov_base with the very start of the header buffers, including space for the qemu vnet_len tag suitable for passt mode. That's ok because we don't actually use these iovecs for pasta mode. However, we do know the mode in udp_sock[46]_iov_init() so adjust these to the beginning of the headers we'll actually need for the mode: including the vnet_len tag for passt, but excluding it for pasta. This allows a slightly nicer way to locate the right buffer to send in the pasta case, and will allow some additional cleanups later. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- udp.c | 36 ++++++++++++++++++------------------ 1 file changed, 18 insertions(+), 18 deletions(-) diff --git a/udp.c b/udp.c index 4e6afff..325adcd 100644 --- a/udp.c +++ b/udp.c @@ -314,8 +314,9 @@ void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s, /** * udp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets + * @c: Execution context */ -static void udp_sock4_iov_init(void) +static void udp_sock4_iov_init(const struct ctx *c) { struct mmsghdr *h; int i; @@ -343,7 +344,11 @@ static void udp_sock4_iov_init(void) for (i = 0, h = udp4_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) { struct msghdr *mh = &h->msg_hdr; - udp4_l2_iov_tap[i].iov_base = &udp4_l2_buf[i].vnet_len; + if (c->mode == MODE_PASTA) + udp4_l2_iov_tap[i].iov_base = &udp4_l2_buf[i].eh; + else + udp4_l2_iov_tap[i].iov_base = &udp4_l2_buf[i].vnet_len; + mh->msg_iov = &udp4_l2_iov_tap[i]; mh->msg_iovlen = 1; } @@ -351,8 +356,9 @@ static void udp_sock4_iov_init(void) /** * udp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets + * @c: Execution context */ -static void udp_sock6_iov_init(void) +static void udp_sock6_iov_init(const struct ctx *c) { struct mmsghdr *h; int i; @@ -383,7 +389,11 @@ static void udp_sock6_iov_init(void) for (i = 0, h = udp6_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) { struct msghdr *mh = &h->msg_hdr; - udp6_l2_iov_tap[i].iov_base = &udp6_l2_buf[i].vnet_len; + if (c->mode == MODE_PASTA) + udp6_l2_iov_tap[i].iov_base = &udp6_l2_buf[i].eh; + else + udp6_l2_iov_tap[i].iov_base = &udp6_l2_buf[i].vnet_len; + mh->msg_iov = &udp6_l2_iov_tap[i]; mh->msg_iovlen = 1; } @@ -685,16 +695,7 @@ static void udp_sock_fill_data_v4(const struct ctx *c, int n, b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh)); if (c->mode == MODE_PASTA) { - /* If we pass &b->eh directly to write(), starting from - * gcc 12.1, at least on aarch64 and x86_64, we get a bogus - * stringop-overread warning, due to: - * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103483 - * - * but we can't disable it with a pragma, because it will be - * ignored if LTO is enabled: - * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80922 - */ - void *frame = (char *)b + offsetof(struct udp4_l2_buf_t, eh); + void *frame = udp4_l2_iov_tap[n].iov_base; if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0) debug("tap write: %s", strerror(errno)); @@ -796,8 +797,7 @@ static void udp_sock_fill_data_v6(const struct ctx *c, int n, b->ip6h.hop_limit = 255; if (c->mode == MODE_PASTA) { - /* See udp_sock_fill_data_v4() for the reason behind 'frame' */ - void *frame = (char *)b + offsetof(struct udp6_l2_buf_t, eh); + void *frame = udp6_l2_iov_tap[n].iov_base; if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0) debug("tap write: %s", strerror(errno)); @@ -1231,10 +1231,10 @@ static void udp_splice_iov_init(void) int udp_init(struct ctx *c) { if (c->ifi4) - udp_sock4_iov_init(); + udp_sock4_iov_init(c); if (c->ifi6) - udp_sock6_iov_init(); + udp_sock6_iov_init(c); udp_invert_portmap(&c->udp.fwd_in); udp_invert_portmap(&c->udp.fwd_out);