From: Roy Marples <roy@marples.name>
Date: Thu, 14 Mar 2019 00:17:26 +0000 (+0000)
Subject: options: add link_rcvbuf variable
X-Git-Tag: v8.0.0~56
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=281818ae04591a3c219623ebb91f22179ba89860;p=thirdparty%2Fdhcpcd.git

options: add link_rcvbuf variable

Sets SO_RCVBUF on the link socket to the designated size.
On a busy system this can be inflated to avoid buffer overflow.

However, dhcpcd *will* cope fine with overflow on NetBSD, OpenBSD
and Linux with a call to getifaddrs(3), but that might be too
heavy weight depending on the libc implementation as most
don't report address flags via this method.
---

diff --git a/src/dhcpcd.c b/src/dhcpcd.c
index f7927140..8986a9b4 100644
--- a/src/dhcpcd.c
+++ b/src/dhcpcd.c
@@ -1128,6 +1128,22 @@ dhcpcd_checkcarrier(void *arg)
 	dhcpcd_handlecarrier(ifp->ctx, LINK_UNKNOWN, ifp->flags, ifp->name);
 }
 
+#ifndef SMALL
+static void
+dhcpcd_setlinkrcvbuf(struct dhcpcd_ctx *ctx)
+{
+	socklen_t socklen;
+
+	if (ctx->link_rcvbuf == 0)
+		return;
+
+	socklen = sizeof(ctx->link_rcvbuf);
+	if (setsockopt(ctx->link_fd, SOL_SOCKET,
+	    SO_RCVBUF, &ctx->link_rcvbuf, socklen) == -1)
+		logerr(__func__);
+}
+#endif
+
 void
 dhcpcd_linkoverflow(struct dhcpcd_ctx *ctx)
 {
@@ -1148,6 +1164,9 @@ dhcpcd_linkoverflow(struct dhcpcd_ctx *ctx)
 		eloop_exit(ctx->eloop, EXIT_FAILURE);
 		return;
 	}
+#ifndef SMALL
+	dhcpcd_setlinkrcvbuf(ctx);
+#endif
 	eloop_event_add(ctx->eloop, ctx->link_fd, dhcpcd_handlelink, ctx);
 
 	/* Work out the current interfaces. */
@@ -1993,6 +2012,9 @@ printpidfile:
 		logerr("%s: if_opensockets", __func__);
 		goto exit_failure;
 	}
+#ifndef SMALL
+	dhcpcd_setlinkrcvbuf(&ctx);
+#endif
 
 	/* When running dhcpcd against a single interface, we need to retain
 	 * the old behaviour of waiting for an IP address */
diff --git a/src/dhcpcd.conf.5.in b/src/dhcpcd.conf.5.in
index f792b15f..70b38ae5 100644
--- a/src/dhcpcd.conf.5.in
+++ b/src/dhcpcd.conf.5.in
@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd September 15, 2018
+.Dd March 8, 2019
 .Dt DHCPCD.CONF 5
 .Os
 .Sh NAME
@@ -429,6 +429,12 @@ globally but needs to be enabled for one interface.
 .It Ic leasetime Ar seconds
 Request a leasetime of
 .Ar seconds .
+.It Ic link_rcvbuf Ar size
+Override the size of the link receive buffer from the kernel default.
+While
+.Nm dhcpcd
+will recover from link buffer overflows,
+this may not be desirable on heavily loaded systems.
 .It Ic logfile Ar logfile
 Writes to the specified
 .Ar logfile
diff --git a/src/dhcpcd.h b/src/dhcpcd.h
index df229fd3..4df57a88 100644
--- a/src/dhcpcd.h
+++ b/src/dhcpcd.h
@@ -145,6 +145,9 @@ struct dhcpcd_ctx {
 	int pf_inet_fd;
 	void *priv;
 	int link_fd;
+#ifndef SMALL
+	int link_rcvbuf;
+#endif
 	int seq;	/* route message sequence no */
 	int sseq;	/* successful seq no sent */
 
diff --git a/src/if-options.c b/src/if-options.c
index 27354629..8f6c0372 100644
--- a/src/if-options.c
+++ b/src/if-options.c
@@ -64,7 +64,7 @@
 #define O_IPV6RS		O_BASE + 4
 #define O_NOIPV6RS		O_BASE + 5
 #define O_IPV6RA_FORK		O_BASE + 6
-// unused			O_BASE + 7
+#define O_LINK_RCVBUF		O_BASE + 7
 // unused			O_BASE + 8
 #define O_NOALIAS		O_BASE + 9
 #define O_IA_NA			O_BASE + 10
@@ -204,6 +204,7 @@ const struct option cf_options[] = {
 	{"lastleaseextend", no_argument,       NULL, O_LASTLEASE_EXTEND},
 	{"inactive",        no_argument,       NULL, O_INACTIVE},
 	{"mudurl",          required_argument, NULL, O_MUDURL},
+	{"link_rcvbuf",     required_argument, NULL, O_LINK_RCVBUF},
 	{NULL,              0,                 NULL, '\0'}
 };
 
@@ -2173,6 +2174,16 @@ err_sla:
 		}
 		*ifo->mudurl = (uint8_t)s;
 		break;
+	case O_LINK_RCVBUF:
+#ifndef SMALL
+		ARG_REQUIRED;
+		ctx->link_rcvbuf = (int)strtoi(arg, NULL, 0, 0, INT32_MAX, &e);
+		if (e) {
+			logerrx("failed to convert link_rcvbuf %s", arg);
+			return -1;
+		}
+#endif
+		break;
 	default:
 		return 0;
 	}