[*] Initial commit

lonetix/bgp/prefix.c

@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+
+/**
+ * \file bgp/prefix.c
+ *
+ * Deal with network prefixes.
+ *
+ * \copyright The DoubleFourteen Code Forge (C) All Rights Reserved
+ * \author    Lorenzo Cogotti
+ */
+
+#include "bgp/bgp_local.h"
+#include "sys/endian.h"
+#include "sys/ip.h"
+#include "numlib.h"
+
+#include <assert.h>
+#include <string.h>
+
+// ===========================================================================
+// Some performance oriented macros to avoid branching during prefix iteration
+
+/// Calculate the minimum size of a possibly ADD_PATH enabled prefix.
+#define MINPFXSIZ(isAddPath) \
+	((((isAddPath) != 0) << 2) + 1)
+
+/// Extract the prefix portion out of a possibly ADD_PATH enabled prefix pointer.
+#define RAWPFXPTR(base, isAddPath) \
+	((RawPrefix *) ((Uint8 *) (base) + (((isAddPath) != 0) << 2)))
+
+/// Calculate maximum prefix width in bits given an address family
+#define MAXPFXWIDTH(family) (((family) == AFI_IP6) ? IPV6_WIDTH : IPV4_WIDTH)  // simple CMOV
+
+// ===========================================================================
+
+char *Bgp_PrefixToString(Afi afi, const RawPrefix *prefix, char *dest)
+{
+	Ipv4adr adr;
+	Ipv6adr adr6;
+
+	switch (afi) {
+	case AFI_IP:
+		memset(&adr, 0, sizeof(adr));
+		memcpy(&adr, prefix->bytes, PFXLEN(prefix->width));
+		dest = Ipv4_AdrToString(&adr, dest);
+		break;
+
+	case AFI_IP6:
+		memset(&adr6, 0, sizeof(adr6));
+		memcpy(&adr6, prefix->bytes, PFXLEN(prefix->width));
+		dest = Ipv6_AdrToString(&adr6, dest);
+		break;
+
+	default:
+		return NULL;  // invalid argument
+	}
+
+	*dest++ = '/';
+	dest    = Utoa(prefix->width, dest);
+	return dest;
+}
+
+char *Bgp_ApPrefixToString(Afi afi, const ApRawPrefix *prefix, char *dest)
+{
+	// NOTE: Test early to avoid polluting `dest` in case of invalid argument;
+	//       hopefully compilers will flatten this function to
+	//       eliminate duplicate test inside switch
+	if (afi != AFI_IP && afi != AFI_IP6)
+		return NULL;  // invalid argument
+
+	dest    = Utoa(beswap32(prefix->pathId), dest);
+	*dest++ = ' ';
+	return Bgp_PrefixToString(afi, PLAINPFX(prefix), dest);
+}
+
+Judgement Bgp_StringToPrefix(const char *s, Prefix *dest)
+{
+	Ipadr      adr;
+	unsigned   width;
+	NumConvRet res;
+
+	const char *ptr = s;
+	while (*ptr != '/' && *ptr != '\0') ptr++;
+
+	size_t len = ptr - s;
+	char  *buf = (char *) alloca(len + 1);
+
+	memcpy(buf, s, len);
+	buf[len] = '\0';
+
+	if (Ip_StringToAdr(buf, &adr) != OK)
+		return NG;  // Bad IP string
+
+	if (*ptr == '/') {
+		ptr++;  // skip '/' separator
+
+		char *eptr;
+		width = Atou(ptr, &eptr, 10, &res);
+
+		if (res != NCVENOERR || *eptr != '\0')
+			return NG;
+	} else
+		width = (adr.family == IP6) ? IPV6_WIDTH : IPV4_WIDTH;  // implicit full prefix
+
+	switch (adr.family) {
+	case IP4:
+		if (width > IPV4_WIDTH) return NG;  // illegal prefix length
+
+		dest->afi = AFI_IP;
+		break;
+
+	case IP6:
+		if (width > IPV6_WIDTH) return NG;  // illegal prefix length
+
+		dest->afi = AFI_IP6;
+		break;
+
+	default:
+		UNREACHABLE;
+		return NG;
+	}
+
+	dest->isAddPath = FALSE;
+	dest->width     = width;
+	memcpy(dest->bytes, adr.bytes, PFXLEN(width));
+	return OK;
+}
+
+Judgement Bgp_StartPrefixes(Prefixiter *it,
+                            Afi         afi,
+                            Safi        safi,
+                            const void *data,
+                            size_t      nbytes,
+                            Boolean     isAddPath)
+{
+	if (afi != AFI_IP && afi != AFI_IP6) {
+		Bgp_SetErrStat(BGPEAFIUNSUP);
+		return NG;
+	}
+	if (safi != SAFI_UNICAST && safi != SAFI_MULTICAST) {
+		Bgp_SetErrStat(BGPESAFIUNSUP);
+		return NG;
+	}
+
+	it->afi       = afi;
+	it->safi      = safi;
+	it->isAddPath = isAddPath;
+	it->base      = (Uint8 *) data;
+	it->lim       = it->base + nbytes;
+	it->ptr       = it->base;
+
+	Bgp_SetErrStat(BGPENOERR);
+	return OK;
+}
+
+void *Bgp_NextPrefix(Prefixiter *it)
+{
+	if (it->ptr >= it->lim) {
+		Bgp_SetErrStat(BGPENOERR);
+		return NULL;  // end of iteration
+	}
+
+	// Basic check for prefix initial bytes
+	size_t left = it->lim - it->ptr;
+	size_t siz  = MINPFXSIZ(it->isAddPath);
+	if (left < siz) {
+		Bgp_SetErrStat(BGPETRUNCPFX);
+		return NULL;
+	}
+
+	// Adjust a pointer to skip Path identifier info if necessary
+	const RawPrefix *rawPfx = RAWPFXPTR(it->ptr, it->isAddPath);
+	if (rawPfx->width > MAXPFXWIDTH(it->afi)) {
+		Bgp_SetErrStat(BGPEBADPFXWIDTH);
+		return NULL;
+	}
+
+	// Ensure all the necessary prefix bytes are present
+	siz += PFXLEN(rawPfx->width);
+	if (left < siz) {
+		Bgp_SetErrStat(BGPETRUNCPFX);
+		return NULL;
+	}
+
+	// All good, advance and return
+	void *pfx = it->ptr;
+	it->ptr  += siz;
+	Bgp_SetErrStat(BGPENOERR);
+
+	return pfx;
+}