diff options
| author | Roy Marples <roy@marples.name> | 2020-08-16 18:52:17 +0100 |
|---|---|---|
| committer | Roy Marples <roy@marples.name> | 2020-08-16 18:52:17 +0100 |
| commit | e5679c5f411e561c31a30fb9cf730ff54b9242ac (patch) | |
| tree | 376202e6df9933671ca5f2e84b0879d1cb422be2 /src/privsep-root.c | |
| parent | cef90b983f28cbe01b9df2e3ba920dcdbd85b60f (diff) | |
| download | dhcpcd-e5679c5f411e561c31a30fb9cf730ff54b9242ac.tar.xz | |
privsep: Set a zero length receive buffer for write only sockets
We cannot use shutdown(2) because they are not connected.
Constantly draining would be a waste of CPU time, so just let
the buffer overflow. To ease the kernel as much as we can, set
a zero length buffer.
The kernel may still allocate a small buffer, but this is kernel
dependant and we're just trying to be helpful.
Diffstat (limited to 'src/privsep-root.c')
| -rw-r--r-- | src/privsep-root.c | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/src/privsep-root.c b/src/privsep-root.c index f1b40745..fe6b1aa6 100644 --- a/src/privsep-root.c +++ b/src/privsep-root.c @@ -638,27 +638,46 @@ ps_root_startcb(void *arg) /* Open network sockets for sending. * This is a small bit wasteful for non sandboxed OS's * but makes life very easy for unicasting DHCPv6 in non master - * mode as we no longer care about address selection. */ + * mode as we no longer care about address selection. + * We can't call shutdown SHUT_RD on the socket because it's + * not connectd. All we can do is try and set a zero sized + * receive buffer and just let it overflow. + * Reading from it just to drain it is a waste of CPU time. */ #ifdef INET if (ctx->options & DHCPCD_IPV4) { + int buflen = 0; + ctx->udp_wfd = xsocket(PF_INET, SOCK_RAW | SOCK_CXNB, IPPROTO_UDP); if (ctx->udp_wfd == -1) logerr("%s: dhcp_openraw", __func__); + else if (setsockopt(ctx->udp_wfd, SOL_SOCKET, SO_RCVBUF, + &buflen, sizeof(buflen)) == -1) + logerr("%s: setsockopt SO_RCVBUF DHCP", __func__); } #endif #ifdef INET6 if (ctx->options & DHCPCD_IPV6) { + int buflen = 0; + ctx->nd_fd = ipv6nd_open(false); if (ctx->nd_fd == -1) logerr("%s: ipv6nd_open", __func__); + else if (setsockopt(ctx->nd_fd, SOL_SOCKET, SO_RCVBUF, + &buflen, sizeof(buflen)) == -1) + logerr("%s: setsockopt SO_RCVBUF ND", __func__); } #endif #ifdef DHCP6 if (ctx->options & DHCPCD_IPV6) { + int buflen = 0; + ctx->dhcp6_wfd = dhcp6_openraw(); if (ctx->dhcp6_wfd == -1) logerr("%s: dhcp6_openraw", __func__); + else if (setsockopt(ctx->dhcp6_wfd, SOL_SOCKET, SO_RCVBUF, + &buflen, sizeof(buflen)) == -1) + logerr("%s: setsockopt SO_RCVBUF DHCP6", __func__); } #endif |